what is constraints ? Defination and examples | easy to learn SQL #

The following constraints are commonly used in SQL: NOT NULL - Ensures that a column cannot have a NULL value UNIQUE - Ensures that all values in a column are different PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table FOREIGN KEY - Prevents actions that would destroy links between tables CHECK - Ensures that the values in a column satisfies a specific condition