Re: Can you SUM(IF) from two different tables at the same time?

"Richard Davey" <rich@fatal-design.com> wrote in message news:20020528225801.70043.qmail@pb1.pair.com... > > In the 5th line I changed "thread.id" to "thread.threadid" so the name was > correct but the same error occurs. Ok, I was guessing at your field names... > to give a perfectly satisfactory result but have no idea if this is > perversing SQL again or not! (grin) When retrieving information from a database, you should expect to get a variable number of records where each record has the same structure. Instead, you were hard-coding a query to get a single record with information about a number of different groups. If you wanted to change the number of groups returned, you would have to change the structure of the query. By getting a record for each group, the structure of the query does not change if you decide to look at a different number of groups - just the data you give to the WHERE clause. > (it at least makes more sense now I guess). > As soon as I add the "where IN" clause it errors. umm... try putting the WHERE clause before the GROUP BY? > Can anyone recommend ANY good books on SQL > query design? I don't want (or care) about database > administration, I just want to know what constitutes a > good database design and lots and lots of query > examples/tutorials. try a Google search for 'database normalization tutorial'; that should get you started. also check out the documentation at www.mysql.com