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Should each table have a primary key?

I read somewhere, saying that every table must have a primary key to execute 1NF.

I have a tbl_friendship table.

The table has 2 fields: "Owner and friend."

The owner and friend fields are foreign keys of the auto increment id field in tbl_user.

Should this tbl_friendship have a primary key? Should I create an auto increment id field in tbl_friendship and make it primary?

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7 answers

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, . http://michaeljswart.com/2011/01/ridiculously-unnormalized-database-schemas-part-zero/

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In the long run, your table will be much easier to manage if it has a primary key. At least you need to uniquely identify each record in the table. A field that is used to uniquely identify each record can also be a primary key.

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Yes, each table must have (at least one) key. Duplication of rows in any table is undesirable for many reasons, so set a limit on these two columns.

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