Many to Many link tables, without PKey defined?

[Crowley16]

Just wanted your opinions on whether it's really needed to define a Primary key in a Many to Many Link table, and why...

Personally, I don't see a need to define a PKey in there, but I could be missing something. Plus, if there is a PKey, then it would probably be a composite of the 2 foreign keys, as I don't see the need to create a autonumber key either...

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[pbrodsky]

You need the primary key (consisting of the 2 FKs) in the link table to aviod having the same record duplicated, which would have no meaning.

 

[r937]

the composite consisting of the two FKs does not need to be a PK, but the composite does need at least to be unique, as pbrodsky pointed out, and the easiest way to do that is by declaring the composite as the PK

the autonumber is useless, and it would only be potentially useful if the table has child tables of its own



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[Crowley16]

cool...

forgot about the unique bit...

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