Example Process Flows - SAS Data Integration Studio 3.3 User's Guide - page 156

2 Click the Mapping tab. By default, the SQL Join transformation maps all columns
in the source tables to the same columns in the temporary output table, as shown
in the following display.
Display 10.5 SQL Join Mapping Tab: Before Extra Columns Are Deleted
However, you need only some of these columns for the report that you want to
create. You can simplify the transformation by deleting the metadata for any
unneeded columns in the target table.