Answers for "how to add a primary key sql table"

add primary key to existing table sql

alter table Persion add primary key (persionId,Pname,PMID)

add primary key to existing table sql

ALTER TABLE `tblauto`
  ADD PRIMARY KEY (`id`);

--

sql server add primary key to existing table with data

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