Suppose we have a header record, with a "closed date" field, and a
detail record with a "vendor" field.
Both files are DDS-created PFs, and the detail file has a LF indexed on
its "parent" field, so it's easy enough to go back and forth between
parent and child.
Now suppose we are doing an SQL SELECT on a join of the header and the
detail, with a WHERE clause involving both fields.
Is there a way to set up an index, whether from SQL or via a new DDS LF,
that would speed up this SELECT?