Question

Explain different constraints to maintain data integrity in sql

Answer 1

Different constraints in mysql are as follows :-
1) primary key : it uniquely identify the records in a table. It can be applied to only one column of the table.
2) foreign key: it is the key applied on column of child table which is referenced to the primary key of parent table.
3) check constraints : it is applied to column or to table to keep check on the records inserted in the table.
4) default constraints : it is applied to table so that if there is any value inserted in table as null, it can replace the value with default value.
Hope it helps you