Re: Is there a difference between these SELECTS's?

Belakimem wrote: > > select * from A where A.numb in ( select numb from B )> > select A.* from B,A where B.numb=A.numb > > Is one more efficient than the other? > > Please also reply by mail, thank you ! They are algebraicly equivalent, but the second one is ineffecient because it performs a full join first. However, a good query optimizer might avoid that. Even the first version may run faster if you insert a DISTINCT in the inner query (depending on your data and, again, the optimizer).