The MERGE statement combines two or more identically sequenced
files on a set of specified keys, and during the process makes records
available, in merged order, to an output procedure or to an output file.
MERGE file-name-1 { [ ON ] { ASCENDING } [ KEY ] { data-name-1 } ... } ...
{ DESCENDING }
[ [ COLLATING ] SEQUENCE [ IS ] alphabet-name-1 ]
USING file-name-2 { file-name-3 } ...
{ OUTPUT PROCEDURE [ IS ] procedure-name-1 { THROUGH } procedure-name-2 ] }
{ THRU }
{ GIVING { file-name-4 } ... }
The COLLATING SEQUENCE clause is parsed, but not implemented yet.