[thelist] what kind of join is this?

[rudy]

> Hopefully that makes more sense.

not to me, but then i'm a weird old fart

let's start with the basics

the login table has one row per person, right?

so PK=logid

the group_membership has one row for every role that a person plays in a
group

so PK=(logid, groupid, role)

so one of the problems you had was to select users who "do /not/ appear in
the group_membership table for a specific group"

okay, that's easy

select logid, first, last, middle
  from login
left outer
  join group_membership
    on login.logid = group_membership.logid
   and group_membership.groupid = 10
 where group_membership.logid is null

basically, you're asking the database to do a left outer join to a specific
groupid, and for those left table logids where there's no match, they will
be returned with a null in the logid of the right table

that's your basic WHERE NOT EXISTS (subquery) construction which mysql does
not support until 4.1


rudy