Add primary key to existing table

Question

I have an existing table called Persion. In this table I have 5 columns:

• persionId
• Pname
• PMid
• Pdescription
• Pamt

When I created this table, I set PersionId and Pname as the primary key.

I now want to include one more column in the primary key - PMID. How can I write an ALTER statement to do this? (I already have 1000 records in the table)

Answer 1

First, drop the constraints of the table and create the new primary constraint to the table

-- Drop the existing primary key constraints

ALTER table Persion 

DROP CONSTRAINT 

PK_persionId

-- Create new primary key constraints

ALTER table Persion 

ADD primary key (persionId, Pname, PMID)

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