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Oracle - SQL - Not Null Constraint
 
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Oracle - SQL - Not Null Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Tutorial 21 - How to Create / Drop Indexes
 
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In the last video, we wrote up the SQL to create three tables: CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, CONSTRAINT users_pk PRIMARY KEY (user_id) ); CREATE TABLE projects( project_id NUMBER, Project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (project_id), CONSTRAINT projects_users_fk FOREIGN KEY (creator) REFERENCES users (username) ON DELETE CASCADE ); CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ); I'm going to increase the size of the users table a bit by adding a first and last name column. CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, first_name VARCHAR2(50 CHAR), last_name VARCHAR2 (50 CHAR), CONSTRAINT users_pk PRIMARY KEY (user_id) ); But before we finish this design, we should consider indexing certain columns. What columns should we index? Well, as a reminder, the columns that are indexed by default are columns with the UNIQUE constraint, and those that are labeled as primary keys. Columns that are not indexed but often should be are those labeled as a foreign key. The column that jumps out the most to me is the creator column of the project table. It's the only foreign key that is not part of some index. Let's fix this by creating our first index. The way we do that is with the CREATE INDEX command. CREATE INDEX projects_creator_ix ON projects (creator) What naming convention are we following for the index? We are naming it by the table name, followed by an underscore, followed by the column, followed by an underscore, followed by an ix (for index). In this situation it does not apply, but if our foreign key column is labeled as UNIQUE, we can add the UNIQUE keyword like this: CREATE UNIQUE INDEX projects_creator_ix ON projects (creator) Now if you want to get rid of an INDEX, you can use this command: DROP INDEX projects_creator_ix Now, if we want to select data from the user table and the project table we can do that much faster. That's because the foreign key and column it references are both indexed and those are the columns we would do the join on. We will discuss how to do joins in a future video. So what are some potential problems with this database design? Overall, it is pretty good. With this design though we need to make sure there is no way for someone to update a user's username. In the next video we are going to discuss why. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 9722 Caleb Curry
Working with Unique Not Null And check Constraints in SQL Server | MSSQL Training | By Mr.Sudhakar L
 
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** For Online Training Registration: https://goo.gl/r6kJbB ? Call: +91-8179191999 💡 Visit Our Website for Classroom Training: https://nareshit.in/sql-server-training/ 💡 For Online Training: https://nareshit.com/course/sql-server-dba-online-training/ #sqlserver #server #programming #course #Tutorials #Training #Videos -------------------------- 💡 About NareshIT: "Naresh IT is having 14+ years of experience in software training industry and the best Software Training Institute for online training, classroom training, weekend training, corporate training of Hadoop, Salesforce, AWS, DevOps, Spark, Data Science, Python, Tableau, RPA , Java, C#.NET, ASP.NET, Oracle, Testing Tools, Silver light, Linq, SQL Server, Selenium, Android, iPhone, C Language, C++, PHP and Digital Marketing in USA, Hyderabad, Chennai and Vijayawada, Bangalore India which provides online training across all the locations -------------------------- 💡 Our Online Training Features: 🎈 Training with Real-Time Experts 🎈 Industry Specific Scenario’s 🎈 Flexible Timings 🎈 Soft Copy of Material 🎈 Share Videos of each and every session. -------------------------- 💡 Please write back to us at 📧 [email protected]/ 📧 [email protected] or Call us at the USA: ☎+1404-232-9879 or India: ☎ +918179191999 -------------------------- 💡 Check The Below Links ► For Course Reg: https://goo.gl/r6kJbB ► Subscribe to Our Channel: https://goo.gl/q9ozyG ► Circle us on G+: https://plus.google.com/+NareshIT ► Like us on Facebook: https://www.facebook.com/NareshIT ► Follow us on Twitter: https://twitter.com/nareshitek ► Follow us on Linkedin: https://goo.gl/CRBZ5F ► Follow us on Instagram: https://goo.gl/3UXYK3
Views: 5420 Naresh i Technologies
Database Design 28 - NOT NULL Foreign Key
 
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Donate!: http://bit.ly/DonateCTVM2. Foreign key columns with NOT NULL as a column characteristic will prevent any rows that do not have a parent primary key. This will force a relationship for every column. More content: http://CalebCurry.com Courses for Download: http://www.udemy.com/u/calebcurry/ Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://Twitter.com/calebCurry Subscribe (it's free!): http://bit.ly/PqPyvH Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 11850 Caleb Curry
Tutorial 12- UNIQUE AND NOT NULL CONSTRAINT
 
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Learn about UNIQUE AND NOT NULL CONSTRAINT in PostgreSQL.
Views: 14664 Programming Guru
Table Constraints in SQL: NOT NULL, DEFAULT, UNIQUE, and CHECK
 
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This SQL tutorial discusses the common constraints one can place on a table: NOT NULL, DEFAULT, UNIQUE, and CHECK, including the purpose of each constraint, as well as how to apply each constraint to a table during table creation. 0:24 NOT NULL Constraint 0:56 DEFAULT Constraint 2:03 UNIQUE Constraint 2:34 CHECK Constraint
Views: 8880 1Keydata
SQL Constraints - NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default
 
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SQL is a standard Structured query language for storing, manipulating and retrieving data in databases. NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default 1) NOT NULL - Ensures that a column cannot have a NULL value 2) UNIQUE - Ensures that all values in a column are different 3) PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table 4) FOREIGN KEY - Uniquely identifies a row/record in another table. The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table. prevents invalid data and destroy links between tables. 5) CHECK - Ensures that all values in a column satisfies a specific condition 6) DEFAULT - Sets a default value for a column when no value is specified 7) INDEX - Used to create and retrieve data from the database very quickly.
Views: 46 R K
Constraints Part-2 NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default
 
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SQL is a standard Structured query language for storing, manipulating and retrieving data in databases. NOT NULL , UNIQUE , PRIMARY KEY , FOREIGN KEY , CHECK , INDEX , default 1) NOT NULL - Ensures that a column cannot have a NULL value 2) UNIQUE - Ensures that all values in a column are different 3) PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table 4) FOREIGN KEY - Uniquely identifies a row/record in another table. The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table. prevents invalid data and destroy links between tables. 5) CHECK - Ensures that all values in a column satisfies a specific condition 6) DEFAULT - Sets a default value for a column when no value is specified 7) INDEX - Used to create and retrieve data from the database very quickly.
Views: 29 R K
NOT NULL, DEFAULT, CHECK Constraints (Domain Integrity) in SQL Server
 
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NOT NULL, DEFAULT, CHECK Constraints (Domain Integrity) in SQL Server Check my blog for more on Constraints and related sample SQL Queries: http://sqlwithmanoj.com/2010/11/23/integrity-constraints/ Check the whole "SQL Server Basics" series here: https://www.youtube.com/playlist?list=PLU9JMEzjCv14f3cWDhubPaddxRvx1reKR Check my SQL blog at: http://sqlwithmanoj.com/ Check my SQL FB Page at: https://www.facebook.com/sqlwithmanoj
Views: 16283 SQL with Manoj
4- Oracle DB - Primary Foreign Unique Not Null Check Composite Keys Table Level and Column Level.avi
 
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Oracle DB - Primary Foreign Unique Not Null Check Composite Keys Table Level and Column Level
Views: 2704 Adel Sabour
Oracle Select Like '% _' With Where Clause تعليم أوراكل
 
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by Mohamed El Desouki - محمد الدسوقى [email protected] Tel :00966 553450836 جامعة سلمان بن عبد العزيز - السعودية - الخرج How to use the Like condition with the Where Clause. البحث عن معلومة غير مكتملة Text Book: Fundamentals of Database Systems, 5th Edition, by Elmasri/Navathe, published by Addison-W oracle create table statement oracle drop table statement oracle constraints database constraints primary key constraint foreign key constraint check constraint null not null constraint unique constraint insert into statement update statement delete statement select statement basic query where clause select where Like '%' Like '_' select where Like
Oracle - SQL - Managing Constraints
 
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Oracle - SQL - Managing Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Tuning with NOT NULL Constraints
 
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Learn how to tune SQL with Constraints! In this lesson (3 of 5), OCM John Watson from SkillBuilders demonstrates how to improve query performance by adding not null constraints. See all lessons, free at http://www.skillbuilders.com/oracle-database-sql-tuning-with-constraints.
Views: 407 SkillBuilders
Oracle Database Indexes: Myths, Tips and Tricks
 
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In this tutorial, OCM John Watson will - via demonstrations - debunk these myths: Myth #1: Oracle Database does not index NULL Myth #2: A search that includes wildcards can't use an index if the wildcard precedes the string. Myth #3: Oracle will not use a function-based index unless the FBI is coded in the predicate. Myth #4: Indexes always help. The more indexes the better. See http://skillbuilders.com/free-oracle-tutorials for gigabytes of free Oracle video tutorials.
Views: 16379 SkillBuilders
Oracle SQL Tutorial 20 - How to Create Composite Primary Keys
 
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This video is going to be a tutorial on how to create composite and compound keys. The difference between a composite and compound key is that a composite key can consist of any columns while a compound key has to consist of columns that are all keys themselves. We will be working with a compound key because we are going to be using the an intermediary table that has two foreign keys. The combination of both of the keys have to be unique. First, if we have any other CREATE TABLE commands, we are going to comment those out. We will space out the CREATE TABLE to have each column on a line, then we will add constraints as needed. CREATE TABLE project_users( project_id, user_id ) Now, let's add the data types: CREATE TABLE project_users( project_id NUMBER, user_id NUMBER } Now, what about some column attributes? I'm going to make both of the columns NOT NULL because we always want the rows to have a user and a project: CREATE TABLE project_users( project_id NUMBER NOT NULL, user_id NUMBER NOT NULL } Now, let's add the foreign key constraints. Now, what do we name these? We are going to add a primary key that covers both of these columns, so I'm going to be a sinner and not give these constraints names: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id), user_id NUMBER NOT NULL REFFERENCES users (user_id) ) Now, the way we have it now is that if we delete a project in the project table, and there are any rows in the project_users table, it will throw an error and prevent deletion. I would prefer for it to also delete any project members. That would make sense because if you delete a project we want it to delete the associate between that project and certain users. The same goes for if we delete a user, we want their association with a certain project to be deleted. To do this, we need to add the ON DELETE command: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, ) Finally, let's learn how to create a compound or composite key. literally, the only difference is that you put a comma and add the second table inside of the parenthesis. CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ) Now, the combination of project_id and user_id cannot be null, is always unique, and has an index. The only thing we should do now is add a few indexes. We aren't done yet...In the next video we are going to figure out what columns would benefit from indexes and we'll add them to it. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 12414 Caleb Curry
46. NOT NULL in SQL (Hindi)
 
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Please Subscribe Channel Like, Share and Comment Visit : www.geekyshows.com
Views: 13795 Geeky Shows
Oracle - SQL - Unique Constraint
 
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Oracle - SQL - Unique Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
SQL 11g Tutorial in Bangla # 47 Constraints: NOT NULL, PRIMARY KEY, FOREIGN KEY, and CHECK
 
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Oracle Database 11g SQL series tutorial in Bangla
Views: 78 Leen's Tech
T-SQL - NOT NULL Constraints
 
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T-SQL - NOT NULL Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited
oracle interview question oracle index function based index
 
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Title: Oracle Interview Question - oracle index related questions - Function based index in oracle Description: Oracle Interview Question - oracle index related questions 1. What is Index? How to create index? 2. What are the types of index? 3. How to find the list of indexes for a given table? 4. Explain B-tree index 5. Explain Bitmap index 6. Explain "Function based" index 7. Explain "Reverse Key" index 8. When to choose what type of index? 9. How to know index is being used? 10. How to monitor index usage? 11. What are the advantages/drawbacks of indexes?
Views: 634 Siva Academy
NULL-Related Functions in Oracle
 
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An overview of some of the functions Oracle provides to handle NULL values in SQL and PL/SQL. For more information see: https://oracle-base.com/articles/misc/null-related-functions Website: https://oracle-base.com Blog: https://oracle-base.com/blog Twitter: https://twitter.com/oraclebase Cameo by Bjoern Rost Blog: http://portrix-systems.de/blog/brost/ Twitter: https://twitter.com/brost Cameo appearances are for fun, not an endorsement of the content of this video.
Views: 2764 ORACLE-BASE.com
Oracle SQL Tutorial 12 - Intro to Constraints
 
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As I believe I've mentioned in an earlier video, a constraint is basically a rule we can put in our database that prevents someone from putting the wrong data in. It protects our relationships and data integrity. Because the goal of these constraints are to protect our data integrity, you may hear them called integrity constraints. There are many integrity constraints we are going to talk about: NOT NULL UNIQUE PRIMARY KEY FOREIGN KRY CHECK There is also the DEFAULT attribute. These are all keywords we can add to our columns that will change the way the database works with our data and also prevents incorrect data. NOT NULL is a constraint you can put on a column that prevents nulls. A null is the absence of a value. When we say null, we are saying that every single row has to have a value for this column. UNIQUE is a constraint that makes every row have a unique value for this column. Now note, this does not require values to be put it, and it will allow multiple rows to be null. Next, we are going to talk about primary keys. What qualifies a column as a candidate key? First, not a single row should have a null for that column. Second, every row must be unique. The primary key constraint is essentially a combination of the NOT NULL constraint and the UNIQUE constraint. The foreign key constraint sets the requirement that any value in this column for any row must match a row in another column. Check constraints allow us to be more strict with what data is allowed in our database. NOT NULL and UNIQUE give some level of restriction, but what if we want something more specific? For example, what if we only want values between 0 and 100? That is where check constraints come in. When using check constraints, you give a boolean expression. A boolean expression is something that can be evaluated to true or false. It will only insert the row if the value you try to put into the row makes the expression evaluate to true. So if you put in a value too great or small, the expression will be false and the data is not allowed to be entered. The default constraint is a value you can give a column, and if for any reason when the row is created in the table a value is not provided, the default value will be given. So for example, we could have a bank account table where the balance defaults to 0. How do you actually implement these constraints when you are creating a table? In the next video we are going to be adding these to our users table. Please be sure to subscribe! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon: http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 23634 Caleb Curry
Oracle Database | Bangla Tutorials 23 :: Constraint Not null
 
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www.facebook.com/oracle.shohag Email : [email protected] Website : www.oraclebangla.com Topics : Constraint Not null
Views: 1035 Oracle Bangla
NOT NULL Constraint in Oracle Database
 
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NOT NULL Constraint in Oracle Database
Oracle SQL Tutorial 19 - ON DELETE (SET NULL and CASCADE)
 
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Welcome everyone! Something you need to consider when you are creating foreign keys is what happens if you delete the parent? As a reminder, the parent is the row that has the value you are referencing in the row that has a foreign key. Why is this something important to consider? It's important because foreign keys need to protect us from two primary things, unacceptable INSERT statements, and unacceptable DELETE statements. Let's see what happens when we try to insert incorrect data into the table with the foreign key: INSERT INTO projects VALUES (1, 'Update website homepage', 'CalebCurry') The response tells us plainly that there is no such user in the users table. So this works correctly. Deleting data on the other hand works a bit differently because the database does not know what you want to do with the child row when you delete the parent from the parent table. By default, we will get an error message that prevents the parent from being deleted, but there are some other options. How do we configure this? This is where the ON DELETE statement comes in. We add the keywords ON DELETE right after the foreign key and then we can give it the option of CASCADE or SET NULL. CASCADE means that if we delete the parent, we are also going to delete the child. In our situation what that means is that if somebody creates a project in our project table and then that persons account gets deleted, all of the projects he owns will also be deleted. CASCADE: CREATE TABLE projects( project_id NUMBER, Project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (project_id), CONSTRAINT projects_users_fk FOREIGN KEY (creator) REFERENCES users (username) ON DELETE CASCADE ) SET NULL will take the value in the child table and get rid of it. What you are left with is NULL. This means that we have an orphaned child. The first thought you might have is that it is a bad thing to have an orphaned child, but in databases that is not always so. In our application if we had it set to SET NULL, when a user account gets deleted the projects would remain in existence they would just lack a creator. This might be a good thing if you are concerned about the long term survival of a project, this might be the route you want to go. It ultimately depends on the application purpose. If you don't like CASCADE or SET NULL, you can leave the entire ON DELETE statement and just have Oracle throw an error when a parent is deleted. As for us, we are going to use ON DELETE CASCADE. We need to use this with extreme caution. If you are not careful, someday you will run a delete a row and that will cascade through you database deleting a bunch of stuff you didn't want to delete. Stuff happens, so make sure you back up your database every once in eternity. Now, in the last video we started with a database design that had three tables. We've only created two in this video. In the next video we are going to create the next one, which is a little special. Then we'll finish things up by adding some indexes. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 18184 Caleb Curry
SQL Tutorial - Clustered Indexes OLTP
 
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Another video brought to you by BeardedDev, bringing you tutorials on Business Intelligence, SQL Programming and Data Analysis. You can now support me on patreon - https://www.patreon.com/beardeddev In this video tutorial we talk all about Clustered Indexes in SQL Server. Indexes allow data to be retrieved quickly but we have to respect a proper indexing strategy as too many indexes can cause DML operations to be come slow. Working with indexes is all about finding the balance between read and write operations on the database. Code featured in the video to allow you to follow along: -- Add Table IF OBJECT_ID(N'dbo.Employees', N'U') IS NOT NULL DROP TABLE dbo.Employees; CREATE TABLE dbo.Employees ( EmployeeId INT IDENTITY(1, 1) NOT NULL , EmployeeFirstName VARCHAR(50) NOT NULL , EmployeeLastName VARCHAR(50) NOT NULL , EmployeeDateOfBirth DATE NOT NULL , EmployeePosition VARCHAR(50) NOT NULL , EmployeeStartDate DATE NOT NULL CONSTRAINT DF_EmployeesNew_EmployeeStartDate DEFAULT (GETDATE()) , EmployeeEndDate DATE NULL , EmployeePayrollId INT NOT NULL ); -- Add Data INSERT INTO dbo.Employees (EmployeeFirstName, EmployeeLastName, EmployeeDateOfBirth, EmployeePosition, EmployeeStartDate, EmployeeEndDate, EmployeePayrollId) VALUES ('Tony', 'Smith', '19860415', 'Sales Executive', '20180101', NULL, 123456) , ('Robin', 'Jones', '19860415', 'Sales Manager', '20180101', NULL, 123457) , ('Michelle', 'Parker', '19860415', 'Sales Executive', '20180101', NULL, 123458) , ('Alex', 'Weaver', '19860415', 'Sales Executive', '20180101', NULL, 123459) , ('Paul', 'Attenborough', '19860415', 'Sales Assistant', '20180101', NULL, 123460) -- Retrieve Data SELECT * FROM dbo.Employees WHERE EmployeeId = 3; -- ADD CLUSTERED INDEX TO EXISTING TABLE ALTER TABLE dbo.Employees ADD CONSTRAINT PK_Employee_EmployeeID PRIMARY KEY (EmployeeId); -- DOES THE TABLE HAVE AN INDEX? SELECT name , syspart.index_id FROM sys.tables AS systab INNER JOIN sys.partitions AS syspart ON systab.[object_id] = syspart.[object_id] WHERE systab.name = 'Employees'; -- WHAT TYPE OF INDEX? SELECT name , [type] , type_desc FROM sys.indexes WHERE name = 'PK_Employees_EmployeeId'
Views: 71 BeardedDev
Oracle - SQL - Foreign Key Constraint
 
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Oracle - SQL - Foreign Key Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Tutorial 13 - How to Add Column Constraints (Attributes)
 
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So far, we have this table declaration: CREATE TABLE users( user_id NUMBER, username VARCHAR(50 CHAR) first_name VARCHAR2(50 CHAR), last_name VARCHAR2(50 CHAR) ) We can run this command see that it works. As we are learning though, we are going to want to be able to recreate our table with different settings and such, but if you try to run this command, it will complain that the table already exists. So we first need to delete this table before we start editing settings. When we get more experienced, we will learn about ways to edit the structure of a table that already exists. To fix this, we can get rid of the table using the DROP TABLE command: DROP TABLE users You can run this every time if you need to practice by adding a semicolon after it. This is how you can tell Oracle that you are putting in another command after it. This is known as a delimiter. When you run the script, it is going to run both commands. Now we can go through and reconsider our table structure. This is fine for starting out because we don't have any important data in our database, but once your database is in production you are not going to want to just drop tables. In the last video we discussed different constraints that you can apply to columns in a database table, but how do you actually apply these when you are creating a table? The first way you define constraints is to put them right after the column in your CREATE TABLE statement. CREATE TABLE users( username VARCHAR2(50 CHAR) NOT NULL ) When we define constraints this way, we usually say we are adding column attributes. If you have two constraints you want to add, you just put one after the other with spaces in between. There is no particular order that is required. CREATE TABLE users( username VARCHAR2(50 CHAR) NOT NULL UNIQUE ) In this situation we have already given the column the NOT NULL and UNIQUE attributes, so we should consider making this a primary key: CREATE TABLE users( username VARCHAR2(50 CHAR) PRIMARY KEY ) As you can see, adding column attributes is super easy. We can add a default like this: CREATE TABLE users( username VARCHAR2(50 CHAR) PRIMARY KEY, account_balance NUMBER DEFAULT 0 ) Note that now we need the comma after the first row. There are a few constraints we did not talk go through an example, specifically foreign keys and check constraints. We will be adding these constraints to our database in future videos. In the mean time, I have a thought for you… Many people prefer to name their column constraints. That way, we can refer to certain constraints by name. For example, we might have a primary key constraint that could be named users_pk. The way we are creating these constraints does not allow for this feature, so in the next video we are going to be discussing different ways to create constraints. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 23598 Caleb Curry
Oracle interview question difference between null functions
 
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Difference between NVL,NVL2, NULLIF and COALESCE NVL function will check whether the first input parameter is null, if first input parameter is null then the function returns the second parameter value as output. NVL2 function will check the first parameter, and return second parameter if the first parameter is not null, otherwise returns third parameter. NULLIF will compare the input parameters ( first and second parameter ), and returns NULL of both are same, otherwise returns the first parameter value. COALESCE, returns the first not null expression in the given input parameters. -------------------------------------------------------------------------------------------------------- List of all the SQL and PLSQL interview questions https://easy-learning-tech.blogspot.com/p/oracle-sql-plsql-interview-questions.html
Views: 1365 Siva Academy
4 - T-SQL - CONSTRAINTS (Restrições) - PRIMARY KEY, NOT NULL, etc - SQL Server
 
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T-SQL - CONSTRAINTS (Restrições) Neste vídeo vamos mostrar como configurar as constraints PRIMARY KEY, NOT NULL, UNIQUE, FOREIGN KEY, CHECK, DEFAULT ao criarmos tabelas em bancos de dados com SQL Server Contribua com a Bóson Treinamentos!: Como contribuir: http://www.bosontreinamentos.com.br/contribuir/ Por Fábio dos Reis Bóson Treinamentos: http://www.bosontreinamentos.com.br Facebook: https://www.facebook.com/bosontreinamentos/ Pinterest: https://br.pinterest.com/bosontreina/ Twitter: https://twitter.com/bosontreina Instagram: https://www.instagram.com/bosontreinamentos/ LInkedin: https://www.linkedin.com/in/f%C3%A1bio-dos-reis-06ba192a/ Outros projetos do autor: Diário do Naturalista: http://www.diariodonaturalista.com.br
Views: 44251 Bóson Treinamentos
Oracle SQL Tutorial -  Handling Null values
 
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In this video, we will see how to handle null values. Retrieving rows where specific column value IS NULL or NOT NULL. Also, we will see functions to handle NULL values. NVL ,NVL2 and NULL IF functions.
Views: 68 Ganesh Anbarasu
SQL Server 26 - PRIMARY KEY, NOT NULL, UNIQUE
 
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In the last video we created our first table, but I want to give SQL Server some extra information so the database knows more about each of the columns. The first thing is to establish the primary key. To do this all we do is add PRIMARY KEY after the column we want to be the primary key. Simple enough. When we add a constraint right after the column like this, it is often called a column attribute. CREATE TABLE Animals( ID INT PRIMARY KEY, Name VARCHAR(50), Species VARCHAR(50) ); Additionally, if you are using an ID column, it is best to have it labeled as the IDENTITY column. That way, SQL Server will automatically increment the number. CREATE TABLE Animals( ID INT PRIMARY KEY IDENTITY, Name VARCHAR(50), Species VARCHAR(50) ); The other attributes we've discussed in this series are NOT NULL and UNIQUE. We can make the name NOT NULL and the species NOT NULL. We don't have a good column for UNIQUE, so let's add one: CREATE TABLE Animals( ID INT PRIMARY KEY IDENTITY, Name VARCHAR(50) NOT NULL, Species VARCHAR(50) NOT NULL, ContactEmail VARCHAR(50) NOT NULL UNIUQE ); You can see that it is very easy to add multiple column attributes to a column. Just separate them by spaces. The order does not matter. Also, when you say primary key the column is automatically NOT NULL and UNIQUE. There are other attributes you can use including DEFAULT, FOREIGN KEY, and SPARSE. DEFAULT will give a value for a column if you do not put anything in yourself. Foreign keys are used to reference other columns. SPARSE is an attribute we haven't discussed. You can use SPARSE if most of the rows are going to have a NULL for a column and it saves storage space, but we will worry about that in another video. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 5782 Caleb Curry
Oracle - SQL - Constraints
 
07:11
Oracle - SQL - Constraints Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Oracle SQL Tutorial 6 - Relationships and Primary and Foreign Keys - Database Design Primer 3
 
29:40
HAPPY VALENTINES DAY!!! Let's talk relationships.. This is the 6th video in your Oracle Database series. We are discussing database relationships which are a key feature of relational database management systems. We first discussed entities and attributes. I talked about how each entity is assigned a table and each attribute is a column within a table. We moved on to the three kinds of relationships. The first was one-to-one. This describes an entity and an attribute. A piece of data that is exclusive to an entity is, by definition, an attribute of that entity. This is stored in one table with the attribute being a column within this table. The second relationship is one-to-many. This relationship is between two entities. The way we properly store this in a database is using a foreign key in the child table. Remember, the child table is the entity on the many side of the one-to-many relationship. Every row within the child table will have a value for the foreign key that references a primary key in the parent table. This assumes that the foreign key field is not optional (NOT NULL). If the foreign key is optional, than a reference is not required but any reference must be valid. The third kind of relationship is a many-to-many relationship. In this situation, we need 3 tables. The many-to-many relationship is broken up into two one-to-many relationships. The intermediary table will associate each entity from one table with the appropriate entities in the other table. There is debate as to whether this table needs a primary key. This is because you can intact use the combination of two foreign keys as a primary key. This works because we will never have two duplicate rows within the intermediary table and the two foreign keys work as a compound key because of this. We finally discussed primary keys and foreign keys. Primary keys are used to keep each row inside of a table unique. If this key is a computer generated number it is known as a surrogate key, otherwise it is known as a natural key. Natural keys have real world meaning. For example, a social security number may work, or an email address (in some situations), etc. Whichever type of key you choose is solely up to you and/or the company you may be working for. HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://Twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 48274 Caleb Curry
BitMap Indexes & Examples
 
11:59
BitMap Indexes & Examples watch more videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Parth Panjab, Tutorials Point India Private Limited
SQL: Delete Vs Truncate Vs Drop
 
08:27
In this tutorial, you'll learn the difference between delete/drop and truncate. PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporation's procedural extension for SQL and the Oracle relational database. PL/SQL is available in Oracle Database (since version 7), TimesTen in-memory database (since version 11.2.1), and IBM DB2 (since version 9.7).[1] Oracle Corporation usually extends PL/SQL functionality with each successive release of the Oracle Database. PL/SQL includes procedural language elements such as conditions and loops. It allows declaration of constants and variables, procedures and functions, types and variables of those types, and triggers. It can handle exceptions (runtime errors). Arrays are supported involving the use of PL/SQL collections. Implementations from version 8 of Oracle Database onwards have included features associated with object-orientation. One can create PL/SQL units such as procedures, functions, packages, types, and triggers, which are stored in the database for reuse by applications that use any of the Oracle Database programmatic interfaces. PL/SQL works analogously to the embedded procedural languages associated with other relational databases. For example, Sybase ASE and Microsoft SQL Server have Transact-SQL, PostgreSQL has PL/pgSQL (which emulates PL/SQL to an extent), and IBM DB2 includes SQL Procedural Language,[2] which conforms to the ISO SQL’s SQL/PSM standard. The designers of PL/SQL modeled its syntax on that of Ada. Both Ada and PL/SQL have Pascal as a common ancestor, and so PL/SQL also resembles Pascal in several aspects. However, the structure of a PL/SQL package does not resemble the basic Object Pascal program structure as implemented by a Borland Delphi or Free Pascal unit. Programmers can define public and private global data-types, constants and static variables in a PL/SQL package.[3] PL/SQL also allows for the definition of classes and instantiating these as objects in PL/SQL code. This resembles usage in object-oriented programming languages like Object Pascal, C++ and Java. PL/SQL refers to a class as an "Abstract Data Type" (ADT) or "User Defined Type" (UDT), and defines it as an Oracle SQL data-type as opposed to a PL/SQL user-defined type, allowing its use in both the Oracle SQL Engine and the Oracle PL/SQL engine. The constructor and methods of an Abstract Data Type are written in PL/SQL. The resulting Abstract Data Type can operate as an object class in PL/SQL. Such objects can also persist as column values in Oracle database tables. PL/SQL is fundamentally distinct from Transact-SQL, despite superficial similarities. Porting code from one to the other usually involves non-trivial work, not only due to the differences in the feature sets of the two languages,[4] but also due to the very significant differences in the way Oracle and SQL Server deal with concurrency and locking. There are software tools available that claim to facilitate porting including Oracle Translation Scratch Editor,[5] CEITON MSSQL/Oracle Compiler [6] and SwisSQL.[7] The StepSqlite product is a PL/SQL compiler for the popular small database SQLite. PL/SQL Program Unit A PL/SQL program unit is one of the following: PL/SQL anonymous block, procedure, function, package specification, package body, trigger, type specification, type body, library. Program units are the PL/SQL source code that is compiled, developed and ultimately executed on the database. The basic unit of a PL/SQL source program is the block, which groups together related declarations and statements. A PL/SQL block is defined by the keywords DECLARE, BEGIN, EXCEPTION, and END. These keywords divide the block into a declarative part, an executable part, and an exception-handling part. The declaration section is optional and may be used to define and initialize constants and variables. If a variable is not initialized then it defaults to NULL value. The optional exception-handling part is used to handle run time errors. Only the executable part is required. A block can have a label. Package Packages are groups of conceptually linked functions, procedures, variables, PL/SQL table and record TYPE statements, constants, cursors etc. The use of packages promotes re-use of code. Packages are composed of the package specification and an optional package body. The specification is the interface to the application; it declares the types, variables, constants, exceptions, cursors, and subprograms available. The body fully defines cursors and subprograms, and so implements the specification. Two advantages of packages are: Modular approach, encapsulation/hiding of business logic, security, performance improvement, re-usability. They support object-oriented programming features like function overloading and encapsulation. Using package variables one can declare session level (scoped) variables, since variables declared in the package specification have a session scope.
Views: 70768 radhikaravikumar
Oracle - PL/SQL - Implicit Cursors
 
04:59
Oracle - PL/SQL - Implicit Cursors https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Validation Rule: Is Not Null
 
02:30
Validation Rule: Is Not Null
Views: 8736 Perins Elearning
Oracle - SQL - Creating Sequences
 
07:31
Oracle - SQL - Creating Sequences Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
ORACLE Technical Interview Question And Answers
 
01:25
ORACLE Technical Interview Question And Answers @ http://www.blog.latestoffcampus.com/2013/11/oracle-technical-interview-question.html ---------------------------------------------------------------------------------------------------------- 1.What are the components of physical database structure of Oracle database? Ans.Oracle database is comprised of three types of files. One or more datafiles, two are more redo log files, and one or more control files. 2.What are the components of logical database structure of Oracle database? Ans.There are tablespaces and database's schema objects 3.How do you switch from an init.ora file to a spfile? Ans.Issue the create spfile from pfile command. 4.What is a CO-RELATED SUBQUERY Ans.CO-RELATED SUBQUERY is one that has a correlation name as table or view designator in the FROM clause of the outer query and the same correlation name as a qualifier of a search condition in the WHERE clause of the subquery. 5.What is SYSTEM tablespace and when is it created? Ans.Every Oracle database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database. 6.What are various joins used while writing SUBQUERIES Ans.Self join-Its a join foreign key of a table references the same table. Outer Join-Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition. Equi-join-Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table 7.What is schema? Ans.A schema is collection of database objects of a user. 8.Give the reasoning behind using an index. Ans.Faster access to data blocks in a table. 9.What type of index should you use on a fact table? Ans.A Bitmap index. 10.What are various constraints used in SQL Ans NULL NOT NULL CHECK DEFAULT 11.What are different Oracle database objects Ans. TABLES VIEWS INDEXES SYNONYMS SEQUENCES TABLESPACES etc 12.What command would you use to encrypt a PL/SQL application? Ans.WRAP 13.What is difference between Rename and Alias Ans.Rename is a permanent name given to a table or column whereas Alias is a temporary name given to a table or column which do not exist once the SQL statement is executed. 14.What is a view Ans.A view is stored procedure based on one or more tables, its a virtual table 15.What are various privileges that a user can grant to another user Ans. SELECT CONNECT
Views: 976 Latestoffcampus
Oracle - SQL - Check Constraint
 
04:15
Oracle - SQL - Check Constraint Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm Lecture By: Mr. Anadi Sharma, Tutorials Point India Private Limited.
Efficient Function Calls From SQL (Part 6) : Function-Based Indexes
 
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The sixth part of a mini-series of videos showing how you can improve the performance of function calls from SQL. In this episode, we look at using function-based indexes to improve the performance of queries that use function calls in the WHERE clause. For more information see: https://oracle-base.com/articles/8i/function-based-indexes https://oracle-base.com/articles/misc/efficient-function-calls-from-sql#functions-in-the-where-clause Website: https://oracle-base.com Blog: https://oracle-base.com/blog Twitter: https://twitter.com/oraclebase Cameo by Ronald Bradford : Blog: http://ronaldbradford.com/blog/ Twitter: https://twitter.com/RonaldBradford Cameo appearances are for fun, not an endorsement of the content of this video.
Views: 1499 ORACLE-BASE.com
13.50 NOT NULL, DEFAULT, CHECK, CREATE DOMAIN
 
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Komplette Liste der Videos und zusätzliches Material auf http://datenbankenlernen.de Informatik, Uni Saarland: Bachelor: http://www.cs.uni-saarland.de/index.php?id=52&L=1&source=1350 Master: http://www.cs.uni-saarland.de/index.php?id=132&L=1&source=1350 Ph.D./Grad School: http://gradschool.cs.uni-saarland.de/&source=1350
Curso de Oracle PL/SQL 12c- Cap 6. Constantes y not null
 
04:38
Puedes hacer el curso completo en este enlace por solo 10$, un gran descuento del precio oficial de 50$ https://www.udemy.com/aprende-oracle-plsql-12c-desde-cero/?couponCode=PROMO-PL 121 clases 8,5 horas de vídeo Múltiples prácticas y ejemplos ¡¡¡Con una máquina virtual ya preparada para trabajar¡¡¡. Aunque durante el curso veremos como instalarlo, para aquellos que queráis ir directamente al grano, hemos creado una máquina virtual en Fedora para que empezeis a trabajar desde el minuto 1.¡¡¡¡Con máquinas virtuales preparadas para el curso!!!! Como ya sabrás, PL/SQL es el lenguaje de desarrollo de Oracle y por tanto uno de los más demandados a nivel laboral en estos momentos. El curso es eminentemente práctico. Mediante ejemplos y ejercicios iremos viendo las características del lenguaje y como puedes utilizarlo. Hay una gran cantidad de prácticas para ayudarte a entender todos los conceptos No necesitas grandes conocimientos, más allá de saber algo de programación y de SQL. Comenzaremos por lo más básicos e iremos profundizando en los distintos capítulos que conforman el curso Aprovecha esta oportunidad
Views: 260 Apasoft Training
mysql tutorial for beginners (6/8) : Indexes
 
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mysql tutorial for beginners (6/8) : Indexes As things stand, the table students works and can be searched without problem by MySQL—until it grows to more than a couple of hundred rows, At that point, database accesses will get slower and slower with every new row added, because MySQL has to search through every row whenever a query is issued. This is like searching through every book in a library whenever you need to look something up. Of course, you don’t have to search libraries that way, because they have either a card index system or, most likely, a database of their own. The way to achieve fast searches is to add an index, either when creating a table or at any time afterward. But the decision is not so simple. For example, there are different index types such as a regular INDEX, PRIMARY KEY, and FULLTEXT. Also, you must decide which columns require an index, a judgment that requires you to predict whether you will be searching any of the data in that column. And even when you’ve decided that, you still have the option of reducing index size by limiting the amount of each column to be indexed. If we imagine the searches that may be made on the students table, it becomes apparent that all of the columns may need to be searched. Anyway, go ahead and add an index to each of the columns, using the commands: ALTER TABLE students ADD INDEX(name(3)); An alternative to using ALTER TABLE to add an index is to use the CREATE INDEX command. They are equivalent, except that CREATE INDEX cannot be used for creating a PRIMARY KEY CREATE INDEX surname ON students (surname(5)); DESCRIBE students; These commands create indexes on both the name and surname columns, limiting name index to only the first 3 characters, and surname index to the first 5 characters. For instance, when MySQL indexes the following name: SAFAA It will actually store in the index only the first 3 characters: SAF This is done to minimize the size of the index, and to optimize database access speed. DESCRIBE command shows the key MUL for each column. This key means that multiple occurrences of a value may occur within that column, which is exactly what we want, as name or surname may appear many times. You don’t have to wait, until after creating a table to add indexes. In fact, doing so can be time-consuming, as adding an index to a large table can take a very long time. Therefore, let’s look at a command that creates the table students with indexes already in place. CREATE TABLE students ( Id_studnet SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, name VARCHAR(10) NOT NULL, surname VARCHAR(20) NOT NULL, email VARCHAR(30) NOT NULL, INDEX(name(3)), INDEX(surname(5)), ,PRIMARY KEY(id_studnet),UNIQUE(email)); Another important index, PK, its single unique key for each student to enable instant accessing of a row. The importance of having a key with a unique value for each row will come up when we start to combine data from different tables. You can add PK, while you create the table at the first time, or later by issuing the following command: ALTER TABLE students ADD PRIMARY KEY(id_student); The last important index, FULLTEXT index Unlike a regular index, MySQL’s FULLTEXT allows super-fast searches of entire columns of text. It stores every word in every data string in a special index that you can search using “natural language,” in a similar manner to using a search engine. It’s not strictly true that MySQL stores all the words in a FULLTEXT index, because it has a built-in list of more than 500 words that it chooses to ignore because they are so common that they aren’t very helpful for searching anyway. This list, called stopwords, includes the, as, is, of, and so on. The list helps MySQL run much more quickly when performing a FULLTEXT search and keeps database sizes down. FULLTEXT indexes can be created for CHAR, VARCHAR, and TEXT columns only. A FULLTEXT index definition can be given in the CREATE TABLE statement when a table is created, or added later using ALTER TABLE (or CREATE INDEX). Adding a FULLTEXT index to the table students for the columns name and surname ALTER TABLE classics ADD FULLTEXT(name,surname); this index is in addition to the ones already created and does not affect them You can now perform FULLTEXT searches across this pair of columns. If you find that MySQL is running slower than you think it should be when accessing your database, the problem is usually related to your indexes. Either you don’t have an index where you need one, or the indexes are not optimally designed. Tweaking a table’s indexes will often solve such a problem. In the next tutorial, we will learn about, using FOREIGN KEY Constraints and how to join tables together. Subscribe for more: ---------------------------------------------------------------------------- https://www.youtube.com/subscription_center?add_user=saf3al2a SWE.Safaa Al-Hayali - saf3al2a
Views: 30210 Safaa Al-Hayali
Oracle SQL Tutorial 4 - Beginner Terms - Database Design Primer 1
 
14:11
The terms covered in this video are: SQL RDBMS Relations NULL Database design Relationships Primary key Foreign key Constraint Indexes Data type HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://Twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 68765 Caleb Curry
Oracle SQL Tutorial 17 - Designing Our Foreign Keys
 
07:47
We are going to continue working with the users table that we've started with, but we are going to add a few tables. Imagine a system where you can create projects. And users can be added to these projects. So this could be some kind of productivity app or a project management solution, think of JIRA. We are going to start with three tables. The first table is going to be a users table that contains all of the information about each user's account. We are then going to have a table that is called projects. Each project will have data about the project and a foreign key that is the creator of the project. This is a situation where the database design depends a lot on the business rules and requirements of the application. Is it appropriate to have only one creator, or can it have multiple creators? We are going to design it with only one creator per project to increase simplicity. The third table is going to be used to record what users are part of certain projects. This situation is a many to many relationship because we've decided that one user can be a part of multiple projects and an individual project can have multiple members working on it. Because this is a many to many relationship, it calls for an intermediary table, project_users. First, we will draw out the user table. We will have a user_id, username, first_name, and last_name. Now, this is our parent table, because it has no foreign keys. Now, this is our parent table, because it has no foreign keys. Other tables are going to be referencing this table, so they would be the children. The project table will have a project_id, title, description, and creator. The column that needs to be a foreign key is the creator. Let's move on to the next table and we'll get back to the foreign key of the project table. The other table was project_users. Knowing that this is an intermediary table, immediately we know that the first two columns are going to be foreign keys to the each of the other tables. Now, let's ask the important questions about the foreign keys. Let's first start with the project table's user column. The first thing we need to ask is what column does it need to reference? Remember, the only options are the columns that are UNIQUE. Our candidates are user_id and username. For now, let's go with username as it makes things easier to work with. Once we go into learning about joins, we will talk about joining things by ID. Different people do it different ways, with the majority using only ID columns for primary and foreign keys, but it's important to be familiar with different ways of doing things. The important thing to remember is that keys should never change, so if we should only reference the username if a user's username will never change. Should the foreign key be labeled UNIQUE? If yes, it means that a user can only create one project. I vote no. Should the foreign key be labeled NOT NULL? If not, it means that a project can exist without a creator. I vote no. Moving on to the next table, I think I'll have the columns reference the project's id and user's id, so we can get some experience referencing surrogate keys. We can apply to these foreign keys the same questions we asked about the other foreign key, and I would encourage you to do so and really think about why. But I can tell you that we are not going to want them to be NOT NULL, but not UNIQUE. Now that we have a pretty decent database design, we can proceed with creating our database. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 11251 Caleb Curry
SQL script to insert into many to many table
 
14:52
Text Article http://csharp-video-tutorials.blogspot.com/2017/02/sql-script-to-insert-into-many-to-many.html Slides http://csharp-video-tutorials.blogspot.com/2017/02/sql-script-to-insert-into-many-to-many_6.html SQL Server Interview Questions and Answers text articles & slides http://csharp-video-tutorials.blogspot.com/2014/05/sql-server-interview-questions-and.html SQL Server Interview Questions and Answers playlist https://www.youtube.com/playlist?list=PL6n9fhu94yhXcztdLO7i6mdyaegC8CJwR All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists In this video we will discuss how to insert data into a table that has many-to-many relationship Create table Students ( Id int primary key identity, StudentName nvarchar(50) ) Go Create table Courses ( Id int primary key identity, CourseName nvarchar(50) ) Go Create table StudentCourses ( StudentId int not null foreign key references Students(Id), CourseId int not null foreign key references Courses(Id) ) Go Students - Id column is identity column Courses - Id column is identity column StudentCourses - StudentId and CourseId columns are foreign keys referencing Id column in Students and Courses tables As you can see, StudentCourses is a bridge table that has many to many relationship with Students and Courses tables. This means a given student can be enrolled into many courses and a given course can have many students enrolled. Below is the question asked in an interview for SQL Server Developer role. Write a SQL script to insert data into StudentCourses table. Here are the rules that your script should follow. 1. There will be 2 inputs for the script Student Name - The name of the student who wants to enroll into a course Course Name - The name of the course the student wants to enroll into 2. If the student is already in the Students table, then use that existing Student Id. If the student is not already in the Students table, then a row for that student must be inserted into the Students table, and use that new student id. 3. Along the same lines, if the course is already in the Courses table, then use that existing Course Id. If the course is not already in the Courses table, then a row for that course must be inserted into the Courses table, and use that new course id. 4. There should be no duplicate student course enrollments, i.e a given student must not be enrolled in the same course twice. For example, Tom must not be enrolled in C# course twice. Answer : To avoid duplicate student course enrollments create a composite primary key on StudentId and CourseId columns in StudentCourses table. With this composite primary key in place, if someone tries to enroll the same student in the same course again we get violation of primary key constraint error. Alter table StudentCourses Add Constraint PK_StudentCourses Primary Key Clustered (CourseId, StudentId) Here is the SQL script that inserts data into the 3 tables as expected Declare @StudentName nvarchar(50) = 'Sam' Declare @CourseName nvarchar(50) = 'SQL Server' Declare @StudentId int Declare @CourseId int -- If the student already exists, use the existing student ID Select @StudentId = Id from Students where StudentName = @StudentName -- If the course already exists, use the existing course ID Select @CourseId = Id from Courses where CourseName = @CourseName -- If the student does not exist in the Students table If (@StudentId is null) Begin -- Insert the student Insert into Students values(@StudentName) -- Get the Id of the student Select @StudentId = SCOPE_IDENTITY() End -- If the course does not exist in the Courses table If (@CourseId is null) Begin -- Insert the course Insert into Courses values(@CourseName) -- Get the Id of the course Select @CourseId = SCOPE_IDENTITY() End -- Insert StudentId & CourseId in StudentCourses table Insert into StudentCourses values(@StudentId, @CourseId) If required, we can very easily convert this into a stored procedure as shown below. Create procedure spInsertIntoStudentCourses @StudentName nvarchar(50), @CourseName nvarchar(50) as Begin Declare @StudentId int Declare @CourseId int Select @StudentId = Id from Students where StudentName = @StudentName Select @CourseId = Id from Courses where CourseName = @CourseName If (@StudentId is null) Begin Insert into Students values(@StudentName) Select @StudentId = SCOPE_IDENTITY() End If (@CourseId is null) Begin Insert into Courses values(@CourseName) Select @CourseId = SCOPE_IDENTITY() End Insert into StudentCourses values(@StudentId, @CourseId) End Use the following statement to execute the stored procedure Execute spInsertIntoStudentCourses 'Tom','C#'
Views: 93093 kudvenkat
CTS interview questions on Oracle SQL and PLSQL
 
06:45
Here are the CTS interview questions on SQL and PLSQL. PL/SQL: What are the activities are you doing daily in your project? Tell me ratio's of sql, pl/sql & Unix? Diff b/w primary key & unique key + not null? What is the use of views? If table dropped, then what happen view? What is index? types of indexes? Which functions are not supported to index? What is save point? What is ora-1555? What are the data types available in pl/sql, not in sql? What is the main use of %type,%rowtype? What is cursor? Types of cursors? Diff b/w explicit cursor & for loop cursor? What is exception? Types of exceptions? What is raise_application_error? How many LONG columns are allowed in a table? What cursor type do you use to retrieve multiple record sets? What is normalization ? What is an index and types of indexes. How many number of indexes can be used per table ? how can we find the select statement is indexed or not? What are wait events. Describe the wait event tables. How do u count no of rows in a table? When do we create bitmap indexes sql query to get zero records from a table having n no of records function can return multiple value? how give give sample coding Difference between NVL, NVL2 and NULLIF Name Salary Abc 50000 Abc 50000 xyz 20000, find the max salary using aggregate function? What are the Diff B/W Cursor and REF Cursor What is pragma_exception_init? Diff b/w triggers & procedures? Can you call procedure in select statement? Restrictions in functions? What is the use of packages? How to drop package body only? Can use pragma_autonamous_tranctions in packages? What is bulk collect? What is nullif()? What is mutating error?  What are the module's , you are working Which will fire default first statement level or row level trigger? What is bulk collect? And any restrictions in bulk collect? What is the use of limit clause in bulk collect? How to debug your code? How to trace error handling? How to find which line error was raised? What are the methods there in save exceptions? What is functional based index? Write syntax? In my next video i will be providing you the answers for each on of this questions. For HCL interview question : https://youtu.be/Pf0lRerwF5U For Global Analytics interview questions : https://youtu.be/joRTF8ZhVwg Please subscribe to my channel here for more videos on recent interview questions of MNC companies. https://www.youtube.com/channel/UCofhGV_j_4cVGa9R08MsuXQ thanks to my subscribers !!
Views: 15577 Oracle PL/SQL

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