We know that a constraint is a restriction or limitation. Similarly, MySQL constraints are used to define rules that limit the data that can enter a table. With the help of constraints, we can basically maintain the accuracy and integrity of the data within the table.
Types of MySQL constraints
There are two types of MySQL constraints −
- Column level constraints −Apply only to specific columns of the table and Constraints that limit column data are called column-level constraints.
- Table-level constraints −Constraints that apply to the entire table and restrict the entire table data are called table-level constraints.
The following are some of the most common MySQL constraints −
- NOT NULL
- UNIQUE
- PRIMARY KEY
- FOREIGN KEY
- CHECK
- DEFAULT
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