Re: two primairy key in one table ?

On Thu, 4 Jul 2002, Angela Luyf wrote:

 > Hello,
 > I have a database model where a many to many relation is used, so i need
 > to create a table with two primary key. Don't know how to solve this in
 > postgress, can't find it in the tutorials, so can anybody help me with
 > this ?

I always create a separate primary key field in the
intermediate table and do a unique index on the
other two fields.

   p1.p1Id                p2.p2Id
      \                     /
       \                   /
        \                 /
         \    t3.t3Id    /
              t3.p1Id
              t3.p2Id

besides of the normal primary and foreign keys I create
an unique index:

    create unique index on t3 (p1Id, p2Id);

Regards Herbie
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Herbert Liechti                                  http://www.thinx.ch
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