TRANSFORM Function Requirements - JOIN setofdatasets

The transform function must take at least one parameter which must take either of two forms:

LEFTformatted like any of the setofdatasets. This indicates the first dataset in the setofdatasets.
ROWS(LEFT)formatted like any of the setofdatasets. This indicates a record set made up of all records from any dataset in the setofdatasets that match the joincondition--this may not include all the datasets in the setofdatasets, depending on which jointype is specified.

The format of the resulting output record set must be the same as the input datasets.