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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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Course Content

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  2. Understanding SDLC Process
    13m 58s
  3. How to use LearnVern
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  4. Client Server Architecture
    5m 18s
  5. How to set up PHP Environment?
    18m 6s

  1. What is Data
    8m 57s
  2. What is Database
    3m 25s
  3. What is DBMS
    14m 25s
  4. SQL Queries and its types
    16m 57s
  5. Data Types in SQL - from 16
    22m 41s
  6. SQL constraints
    10m 52s
  7. Create, Drop & Show Database
    13m 40s
  8. SQL Create Table
    13m 53s
  9. SQL Insert & Select Statement
    26m 56s
  10. Operators in SQL
    6m 47s
  11. In & NOt in Condition
    7m 4s
  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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  4. Assignment : Operators
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  3. $_FILES & $_ENV in PHP
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  2. switch case in PHP
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  3. Assignment : Conditional Statements
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  1. Functions in PHP
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  2. Call by value vs Call by reference in PHP
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  3. Assignment : Functions
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  1. Array Functions in PHP
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  2. Array in PHP
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  3. Assignment : Array
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  1. String and its Functions in PHP
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  2. Assignment : String
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  1. Loops in PHP
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  2. More examples on Loops in PHP
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  3. Assignment : Loops
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  1. Cookies in PHP
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  2. Session in PHP
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  1. Header Function in PHP
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  2. Assignment : Header Functions
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  1. Date and Time functions 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
    32m

  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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