Merge combines two sorted files with identical record layouts into a third file. The combined data in the new output file is sorted on a key character field.
The primary and secondary tables must have identical layouts, although the field names can differ. They must also have a common key field. For example, you could combine two files with identical record layouts from different time periods or different company branches. Only the secondary file needs to be physically sorted. The primary file can be presorted during the execution of the command.
For more information on the Merge command see Merge.