Missing table entries

Does anyone know of a way WITHIN sql for identifying missing entries in a table? I have a master table which contains a unique (indexed) code field. This code is also used in the detail table. Each code should have *at least* one entry in the detail table, but it may have more than one. How do I find those codes which have *no* entry in the detail table? I can see the missing rows if I do something like: select table1.code, table2.code from table1, outer table2 where table1.code=table2.code but I have to search the output to find the gaps. The other approach I have used is to UNLOAD the code from each table to a file and use the UNIX command comm to find the missing codes. Does anyone have a better approach? ** Opinions expressed are my own and not necessarily those of my employer ========================================================================= Barry Toomey Phone +353-1-2822333 AT&T Network Systems Ireland Fax +353-1-2822864 Corke Abbey Avenue, email: bt@irl3b2c.att.com Bray, uunet: att!irl3b2c!bt Co. Dublin Ireland =========================================================================