RE: SQL Question - Merging files or result sets?

Adam, a little heads up on your example.

UNION implicitly performs DISTINCT processing, UNION ALL does not.
Besides potential functional difference (i.e. different end result set),
there is a tremendous difference in performance between the two.

I find that in most cases developers really want UNION ALL, but forget to
specify the ALL identifier.

HTH, Elvis

Celebrating 11-Years of SQL Performance Excellence on IBM i5/OS and OS/400
www.centerfieldtechnology.com


-----Original Message-----
Subject: Re: SQL Question - Merging files or result sets?

I think that UNION will do the trick. Perhaps you could do something like:

selectA = 'SELECT <the fields> FROM fileA WHERE <criteria>'
selectB = 'SELECT <the fields> FROM fileB WHERE <criteria>'
order = ' ORDER BY <ordering fields>'

if (search = both A and B)
query = selectA + ' UNION ' + selectB + order

elseif (search = A only)
query = selectA + order

else
query = selectB + order