Use the following Query to check whether the Table does have "Primary Key" or not.
Lets assume its Employee Table here. the Query is as Follows :
Example :
IF OBJECTPROPERTY( OBJECT_ID( '[dbo].[Employee]' ), 'TableHasPrimaryKey' ) = 1 PRINT '[dbo].[Employee] table has a primary key.' ELSE PRINT '[dbo].[Employee] table has no primary key.'