Constraints are set of rules used to restrict the type of data that can go into a table, to preserve the accuracy and integrity of the records internal the table.

The different types of constraints in DBMS are as follows:-
  • NOT NULL:-it makes sure that column does not hold a NULL value.
  • UNIQUE:- It invokes a column to have a UNIQUE value
  • DEFAULT:-gives the default value to the column
  • CHECK:-specify the range of values for a column
  • Key Constraints
  • PRIMARY KEY:-it diagnose each and every record in a table
  • FOREIGN KEY:- it points to the primary key of any other table.
BY Best Interview Question ON 18 Mar 2020