PHP MySQL - Select members with where-clause statements from different tables

Question

I've been Googling for most of my day now but I can't seem to find the right answer. Maybe because I don't really know in which direction to look (join? exist?). What I have is 3 tables:

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There is a table named 'groups' and 'languages' containing the actual group- and language data but that's not important right now.

The user should be able to generate a list with all members, depending on the selected groups and/or languages. The groups/languages that the user selected are saved in two separate array's containing the IDs ( $aGroups and $aLangs ).

What I want/need is to SELECT * FROM members WHERE ...

And that's where I got stuck. I've tried joins, I've tried IN() , I've tried EXIST but nothing seems to work right.

Any help is greatly appreciated!

Answer 1

I think you just need some brackets:

//assuming you have ids stored in $lang and $group
SELECT * FROM members WHERE (SELECT group_id FROM group_members WHERE member_id=members.id)='$group'
AND (SELECT lang_id FROM language_members WHERE member_id=members.id)='$lang' 

The trick is "members.id", DB will call subquery for every member to find out if the condition for group and lang is met.

Answer 2

If you want to select members by languages and groups, you can do something like this :

$query = "select * from members as m 
left join group_members as gm on gm.member_id = m.id 
left join language_members as lm on lm.member_id = m.id";
if(isset($aGroups)) {
  $query .= " where group_id in (".implode(",", $aGroups).")";
  if(isset($aLangs)) {
    $query .= " and language_id in (".implode(",", $aLangs).")";
  }
} 
elseif(isset($aLangs)) {
  $query .= " where language_id in (".implode(",", $aLangs).")";
}

Answer 3

Select m.* FROM members m, group_members gm, language_members lm
WHERE
lm.member_id=m.id AND
m.id=gm.member_id AND
<<<< START YOUR OWN WHERE HERE.