SQL Tutorial - 10 SQL Constraints Parent Child Relationship Oracle Primary Key Foreign Key

Constraints are the rules which applied on data columns on table. These are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the database. Constraints could be column level or table level. Column level constraints are applied only to one column, whereas table level constraints are applied to the whole table.

Types of Constraints

1. Unique

2. Not null

3. Primary Key

4. Check

5. Foreign Key