sql - Comparing 2 tables , find not existing "id" -

i have speed problem when comparing 2 tables. let's have following tables.

table a 14,000 records

name(varchar) , join_id(int)

table b 54,209 records

second_name , join_id(int)

now want find rows exists in table , not in b connected joint_id ordered random ( sort of )

i tried following :

 select a.name , b.second_name          left outer join b on a.joint_id = b.joint_id     b.joint_id null     limit 0,10 

the query took ages , messing server , question ;

is there faster way accomplish ?

edit : removed rand() , can solved otherwise. still have same problem. try out suggestions below , see if can improve query time.

notice gave second column fixed value of null, since when b not exist, b.second_name => null. crux of problem order rand() require full scan put rand() against each record. cannot avoid table scan.

select a.name , null second_name  not exists (select * b a.joint_id = b.joint_id) order rand()  limit 0,10; 

you possibly make faster not having drag columns table a, assuming have id on table a. http://dev.mysql.com/doc/refman/5.0/en/order-by-optimization.html

select a.name , null second_name  a.id in (     select id     not exists (select * b a.joint_id = b.joint_id)     order rand()     limit 0,10)