mysql queires and UNION??

[grant.hayman]

I have an advertsers database which baisicly holds banner code and some parameters to distinguish placement and usergroups etc.

I have have 4 ad slots which very in size, shape and how many banners it will hold etc.

So to call the banner code i need 4 queries, one for each slot. Which means 4 db hits.

If i write the query as a UNION query and order the result as i need will this be a lot better for vbulletin for overhead etc or since it is doing 4 selects anyway does it really make much difference.

Baisicly do UNION queries help with vbulletin overhead is it classed as 1 hit to the db instead of 4.

Thanks

Grant