Andrew, Another approach, one that does not require you to know before constructing the query how many eligible subjects there are, is not to use a union at all:
SELECT * FROM ( SELECT ... , zip FROM participants WHERE (typenr = 1 and <eligibility criteria) OR (typenr = 2) ORDER BY (typenr = 1 and <eligibility criteria>) DESC LIMIT 200 ) p1 ORDER BY zip; The inner query gives you all of the records that meet the eligibility criteria, plus all of the records that have typenr = 2, in the order of whether or not they meet the criteria (as a boolean value) and truncates it at 200 records. The outer query then re-sorts this result in zip order. This seems, to me, much more flexible than using a UNION query. -- -Josh Berkus Aglio Database Solutions San Francisco ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
