SQL EXCEPTION JOIN

I have three files (orderinfo, deliveryinfo and itemlines). The three files entries shall exist as 1 to 1 to many.

The files contains orders from 10+ years. Thus data has been migrated several times by various people.

I have discovered that the one-to-one-to-many rule has been broken for many orders. I wrote a pgm to check the file’s ordernumbers against the other files to find the ordernumbers with missing records. It turned (as expected) out to be a very time-consuming task.

I challenged myself to write an sql to do the job, assuming that it will perform better, but… Alas, I must admit that I have not yet been able to write the sql. Can anybody help ?