Create a MySQL table with a primary key

A primary key uniquely identifies a row in a table. One or more columns may be identified as the primary key. The values in a single column used as the primary key must be unique (like a person’s social security number). When more than one column is used, the combination of column values must be unique.
When creating the contacts table described in Create a basic MySQL table, the column contact_id can be made a primary key using PRIMARY KEY(contact_id) as with the following SQL command:

Additional columns can be identified as part of the primary key with a comma separated list in the PRIMARY KEY command, like PRIMARY KEY (contact_id, name).

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