Answers

2016-03-29T18:36:59+05:30

Primary Key:

Can be only one in a tableIn some DBMS it cannot be NULL - e.g. MySQL adds NOT NULLPrimary Key is a unique key identifier of the record

Unique Key:

Can be more than one unique key in one tableUnique key can have null valuesIt can be a candidate keyUnique key can be null and may not be unique
0
2016-03-29T18:39:19+05:30

primary Key:

Can be only one in a tableIn some DBMS it cannot be NULL - e.g. MySQL adds NOT NULLPrimary Key is a unique key identifier of the record

Unique Key:

Can be more than one unique key in one tableUnique key can have null valuesIt can be a candidate keyUnique key can be null and may not be unique
0