A primary key constraint is a combination of a NOT NULL constraint and a UNIQUE constraint. This constraint ensures that the specific column for a table has a unique identity.
Primary key constraints. A primary key (PK) is a single column or combination of columns (called a compound key) that uniquely identifies each row in a table.
Following example to check if a primary key exists
CREATETABLEPRODUCT ( IDINTNOTNULLIDENTITY(1,1), SKUVARCHAR(20)NOTNULL, TITLEVARCHAR(200)NOTNULL, PRICEMONEYNOTNULL, DESCRIPTIONVARCHAR(2000) NULL, DTCREATEDATETIMENULL CONSTRAINTpk_Product_IDPRIMARYKEY (ID) ) IFOBJECT_ID('dbo.pk_Product_ID')ISNULL ALTERTABLEPRODUCTADDCONSTRAINTpk_Product_IDPRIMARYKEY(ID) ELSE PRINT'Product table already has primary key' DROPTABLEPRODUCT |
