What are MySQL constraints?

MySQLMySQLi Database

As we know that constraint is a kind of limitation or restriction. Similarly, MySQL constraints are used to define some rules that limit the data that can go into a table. With the help of constraints, we can basically maintain the accuracy and integrity of the data inside the table.

Types of MySQL constraints

MySQL constraints are of two types −

  • Column Level constraints − The constraints which are applied only to a particular column of the table and limits only column data are called column level constraints.
  • Table Level constraints − The constraints which are applied to the whole table and limits whole table data are called table-level constraints.

Followings are some most common MySQL constraints −

  • NOT NULL 
  • UNIQUE 
  • PRIMARY KEY 
  • FOREIGN KEY 
  • CHECK
  • DEFAULT
raja
Published on 16-Feb-2018 11:42:46
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