If you want to compare a field to a list of constants which reside in a file, MFX’s join facility could be used instead of INCLUDE or OMIT.
For instance, if you needed to compare a field in a master file to a long list of airport codes, you would normally need to create an INCLUDE or OMIT condition such as
1,3,CH,EQ,C’JFK’,OR,1,3,CH,EQ,C’LAX’,OR,1,3,CH,EQ,C’DFW’,OR,1,3,CH,EQ,C’ ATL’,...
(or the shorthand equivalent 1,3,CH,EQ,L(C’JFK’,C’LAX’,C’DFW’,C’ATL’,...)). But if all the codes were in a second file in the form
....JFK..… (record 1)
....LAX..… (record 2)
....DFW.… (record 3)
....ATL..… (record 4)
................ ...
you could easily use the join facility to read the file directly and compare a field in each record to a field in the master file. This technique would perform the equivalent processing, eliminating the need for a lengthy control statement.
See Using Join Processing To Copy a Large Number of Master File Records for an example of how to do this with MFX’s join facility.