MySQL exclusion, table joining question

[Anon]

I've got two tables, each with a string of ids.

Table B is a subset of Table A.

Table A id values (eg) 1,2,3,4,5,6,7,8,9,10
Table B id values 1,5,7

What's the quickest way of selecting one value in Table A that is NOT present in Table B? I've got a loop setup to query all the values in Table A, then do a select on Table B. If the result is negative the loop breaks and the result is returned. But this is getting CPU intensive since I have thousands of values. Any help would be appreciated.

[bastien]

depending on DB you could try a subselect

select * from tableA where id not in (select id from table😎

This may not work for MySQL depending on version you have....

bastien

[Anon]

Thanks for the reply, got something that will work in MySQL from devshed:

select * FROM table_A as a LEFT JOIN table_B as b ON a.id=b.id WHERE ISNULL(b.id) ORDER BY rand() LIMIT 1

Works fine and is quite fast.