check, not null,unique

Answer Posted / prasanthi

Check Constraint:

The CHECK constraint is used to limit the value range that
can be placed in a column.

not null constraint:

if we give not null constraint to any column it will not
accept null values.

Unique Conatraint:

Unique key is similar to primary key but it accepts one
null value.
For o column Setting Unique key+Not NULL we can make
Primary Key.

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