I'm asking this as a more general question on which will perform better. I'm trying to get a set of comments and their score/rankings from two tables.
*comments* cid (integer, primary key) title body *comment_ratings* cid (integer, primary key) uid (integer, primary key) score *Option 1* (Single group by query) select c.cid,c.title,c.body,coalsece(sum(r.score),0) as score from comments c left outer join comment_ratings r on c.cid = r.cid group by c.cid,c.title,c.body; *Option 2* (Two simple queries) select cid,title,body from comments; select cid,sum(score) from comment_ratings; I know that in general you always want to keep the number of queries to a minimum and that Option 1 is the most logical/preferred way to proceed. However, I've greatly simplified Option 1. In practice I'm going to be pulling a lot more columns and will be inner joining to additional tables. *So my real question is whether having a lot of items in the group by clause will have an adverse effect on performance.* Thanks in advance, Jonathon
