Answers for "add primary key to existing table sq;"

change primary key sql

ALTER TABLE <Table_Name>
DROP CONSTRAINT <constraint_name>

ALTER TABLE <Table_Name>
ADD CONSTRAINT <constraint_name> PRIMARY KEY (<Column1>,<Column2>)

sql server add primary key to existing table with data

ALTER TABLE Production.TransactionHistoryArchive
   ADD CONSTRAINT PK_TransactionHistoryArchive_TransactionID PRIMARY KEY CLUSTERED (TransactionID);