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What are MySQL constraints?

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Aug 24, 2023 pm 06:17 PM

MySQL 的约束是什么？

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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