[kevincox]

HAVING is a hack. Because SQL has such an inflexible pipeline we needed a second WHERE clause for after GROUP BY.

It would be nice if we could have WHERE statements anywhere. I would like to put WHERE before joins for example. The optimizer can figure out that the filter should happen before the join but it is nice to have that clear when looking at the code and it often makes it easier to read the query because you have to hold less state in your head. You can quickly be sure that this query only deals with "users WHERE deleted" before worrying about what data gets joined in.

[bonzini]

You can put WHERE before joins using nested queries, i.e. "FROM (SELECT * FROM users WHERE deleted") INNER JOIN ...".