add primary key to existing table sq; code example
Example 1: change primary key sql
ALTER TABLE <Table_Name>
DROP CONSTRAINT <constraint_name>
ALTER TABLE <Table_Name>
ADD CONSTRAINT <constraint_name> PRIMARY KEY (<Column1>,<Column2>)
Example 2: sql server add primary key to existing table with data
ALTER TABLE Production.TransactionHistoryArchive
ADD CONSTRAINT PK_TransactionHistoryArchive_TransactionID PRIMARY KEY CLUSTERED (TransactionID);