Question

I have to join 2 tables which are currently holding more than 200K data each. I have members and orders table. I would like to get members who didn’t order anything.

I tried following SQL queries;

Structure (just listing what I need)

ORDERS                  MEMBERS
id                      id
member_id               fullName
                        email
                        landLine
                        cellPhone

Query1

$sql  = 'SELECT '.PREFIX.'members.fullName
           , '.PREFIX.'members.email
           , '.PREFIX.'members.landLine
           , '.PREFIX.'members.cellPhone, ';
$sql .= 'FROM '.PREFIX.'members';
$sql .= 'LEFT JOIN ';
$sql .= PREFIX.'orders';
$sql .= ' ON ';
$sql .= PREFIX.'members.id = '.PREFIX.'orders.member_id';
$sql .= ' WHERE '.PREFIX.'orders.member_id IS NULL LIMIT 50';

Query 2

$sql2  = 'select id, fullName, email, landLine, cellphone 
          from '.PREFIX.'members 
          where '.PREFIX.'members.id not in 
             (select member_id from '.PREFIX.'orders) 
          LIMIT 50';

Query 3

$sql3  = 'select id, fullName, email, landLine, cellphone 
          from '.PREFIX.'members m 
          where not exists 
            (select null from '.PREFIX.'orders o where s.members_id = o.id) 
          LIMIT 50';

All 3 queries so far didn’t work. More than a minute passed, I am still waiting for the results.

What is the most elegant way to do this? Which one is faster and using less resources? I don’t see anything wrong here why it would work but for some reason it just can’t list.

Thank you for your help in advance.

Answer 1

I should try

SELECT id, fullName, email, landLine, cellphone 
FROM members
WHERE id NOT IN
    (SELECT DISTINCT member_id FROM orders)
LIMIT 50

Be sure to put indexes on members.id and orders.member_id.