Обсуждение: SQL subquery question
I think this can be done with one SQL statement, but I'm not sure. I have two tables: table t contains key k, another field f, and a bunch of other stuff. In a poor design decision, table tsubset contains a small number of "pointers" to t. I should have used the k column; instead I used the f column (it is unique, but not the primary key). I want to fix this. I altered tsubset to have two columns, f and k, where k will be a foreign key referencing t(k). I now need to copy all the k values from t to tsubset. I think I want to do something like this: foreach f in tsubset update tsubset set k=(select k from t, tsubset where t.f=f); end Can this be done with one SQL statement?
Rick Schumeyer wrote: > foreach f in tsubset > update tsubset set k=(select k from t, tsubset where t.f=f); > end > > Can this be done with one SQL statement? I think you mean update tsubset set k = t.k from t where t.f = f; -- Alban Hertroys alban@magproductions.nl magproductions b.v. T: ++31(0)534346874 F: ++31(0)534346876 M: I: www.magproductions.nl A: Postbus 416 7500 AK Enschede // Integrate Your World //
Thanks for the suggestion...it needed only one small change: update tsubset set k = t.k from t where t.f=tsubset.f; Thanks! Alban Hertroys wrote: > Rick Schumeyer wrote: > >> foreach f in tsubset >> update tsubset set k=(select k from t, tsubset where t.f=f); >> end >> >> Can this be done with one SQL statement? >> > > I think you mean > update tsubset set k = t.k from t where t.f = f; > >