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Why use primary keys?

What are the primary keys used in addition to identifying a unique column in a table? Could this not be done simply using the auto-increment constraint for the column? I understand that PK and FK are used to link different tables, but can this be done simply by using join?

Basically, what does a database do to improve performance when connecting using primary keys?

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Mainly for referential integrity with foreign keys. When you have a PC, it will also create an index behind the scenes, and thus you do not need to scan tables when looking for values

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Source: https://habr.com/ru/post/1731056/

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