Constraint is defined as a part of individual attribute or column. In terms of computer programming, constraints relation are stated in the form of variable. Basically, constraint is the rule that are use for optimization purpose.
There are different types of constraints that are:
Primary key constraint : It is defined as, the combination of columns which uniquely identify each data in the database table.
Unique constraint : Unique constraint are used to ensure that all the values in the column table in the database are must be different.
Not null constraint : It basically prevent all the null values from entering into one or more than one column in a table.
