How can i find difference in 2 tables in different databases with same structure

[rizwan6feb]

I am developing an application in VB.net 2005 that synchronizes two mysql databases of same structure. I have done most of the work but having problem in finding the difference in records in 2 tables. Let me explain the scenario

There is a table in the local database having name "user". The same table exists in the online version of the database. I want to find the difference of records in the 2 tables so that i can delete surplus users from the online version of the database. I am trying something like this, which is not working

DELETE FROM localdb.user
WHERE userid NOT 
IN (
SELECT group_concat( userid
SEPARATOR  ','  ) 
FROM onlinedb.user
)
LIMIT 0 , 30
 

I can't afford to select all the records and then find the difference betwen the 2 tables

[Atli]

You should be able to simply do:

DELETE FROM localdb.user
WHERE userid NOT 
IN (
  SELECT userid
  FROM onlinedb.user
)
LIMIT 0 , 30