Subject Re: [firebird-support] JOINs vs WHERE
Author Jonathan Neve

I'm not fully acquinted with all the nitty-gritty, but the two I use
most often are "JOIN" and "LEFT OUTER JOIN". The former is simply what
you would expect, whereas the latter has the feature that it does not
exclude records that do not match the join conditions, it simply returns
the joined fields as null. Thus, if you have a nullable field, you can
display in one query all records, wheather this field is null or not,
and do a lookup into the corresponding lookup table to get extra
information when it isn't null. This avoids using lookup fields on the
client side, which is usually slower.

Hope this helps,
Jonathan Neve.