It is a rule used to limit the type of data that can insert into a table, to maintain the integrity and accuracy of the data inside the table.

It can be divided into two types.

  • Column level constraints
  • Table-level constraints

These are the most common constraints that can be applied to a table.

  • NOT NULL
  • DEFAULT
  • UNIQUE
  • PRIMARY KEY
  • FOREIGN KEY etc
BY Best Interview Question ON 27 Jan 2019