The ADD CONSTRAINT keyword can be used to create a new constraint on an existing table, using the ALTER TABLE statement.
The below SQL adds a primary key constraint, based on a single column.
ALTER TABLE customers
ADD CONSTRAINT PK_Customer PRIMARY KEY (customer_id);The below SQL adds a primary key constraint, based on multiple columns (namely id and name).
ALTER TABLE customers
ADD CONSTRAINT PK_Customer PRIMARY KEY (customer_id, customer_name);If you find the content useful and like to share it with others, you can click the below link to share on social platforms.
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