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SQL constraints

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SQL constraints are rules that a table's data must follow. The type of data that can be entered into a table is limited by constraints. This ensures that the data in the table is accurate and reliable. The action is cancelled if there is a conflict between the constraint and the data action.

When no value is supplied for a column, the DEFAULT Constraint provides a default value. UNIQUE Constraint ensures that every value in a column is unique. Each row/record in a database table is uniquely identified by the PRIMARY Key. FOREIGN KEY identifies a row/record in any database table in a unique way.

A constraint is defined as something that imposes a limit or restriction on something or prohibits something from happening. The fact that there are only so many hours in a day to complete something is an example of a restriction. A check is a device that restricts, limits, or regulates something.

Constraints are required for developing respect for other people's opinions and beliefs. It is required for the development of a society. Absence of restraint would result in the imposition of stronger groups' views and ideas, eventually leading to war. Controlling violence and resolving conflicts necessitates the use of constraints.

Constraints are used to ensure data integrity when updating, deleting, or inserting data into a table. If any operation in the database does not follow the rules stated by the constraint after it is placed, the operation is aborted.

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Anish Narang
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Best Course in Market till now

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Nitish Kumar Sharma
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Meet Shah is the worst teacher i have found in learnvern platform please replace his video with some other teacher he is unable to explain concept properly and sometimes he explain concept incorrect.

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Sonu sonu
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very good

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Islam Web
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Nice

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Ravi Ranjan Tiwari
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I am very happy that I am studying from LearnVern.

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Muhammad Talha
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help full.

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Prince Bavishi
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nice work

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sonakshi Raj
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Excellent

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Shibu Kumari
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Very Good

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Rajiv Kumar Singh
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It would have been better if you could have provided the resource/source_code files of the CRUD operations so that we could have cross verified our code with yours.

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  2. Understanding SDLC Process
    13m 58s
  3. How to use LearnVern
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  4. Client Server Architecture
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  5. How to set up PHP Environment?
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  1. What is Data
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  2. What is Database
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  3. What is DBMS
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  4. SQL Queries and its types
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  5. Data Types in SQL - from 16
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  6. SQL constraints
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  7. Create, Drop & Show Database
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  8. SQL Create Table
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  9. SQL Insert & Select Statement
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  10. Operators in SQL
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  11. In & NOt in Condition
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  12. Null & Not Null Condition
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  13. Clauses in SQL
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  14. Understanding Having, Distinct & Group by
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  15. Update & Delete in SQL
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  16. Alter table command in SQL
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  17. MySQL Rename truncate Drop
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  18. Understanding Foreign key
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  19. MySQL joins
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  20. MySQL views
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  21. MySQL Function
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  22. MySQL Procedure
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  23. MySQL Trigger
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  24. Normalization
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  25. Assignment : MYSQL
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  1. Understanding PHP Program structure Comments in PHP
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  1. Variables in PHP
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  1. Arithmetic & Assignment Operators in PHP
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  2. Comparison & Logical Operators in PHP
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  3. Ternary Operator in PHP
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  2. Assignment : Date Time Functions
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  1. Include & Require Statement in PHP
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  1. Error Handling in PHP
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  1. File Upload in PHP
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  1. Database Connection in PHP Part 1
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  2. Database Connection in PHP Part 2
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  1. SQL Injection in PHP
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  1. Crud - Registration and DB connection Part 1
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  2. Crud - Registration and DB connection Part 2
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  3. Log in Operation
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  4. Read Operation
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  5. Update Operation Part 1
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  6. Update Operation Part 2
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  7. Log out Operation
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  1. MySQL Interview Question 1
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  2. MySQL Interview Question 2
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  3. MySQL Interview Question 3
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