Hi,
You can update a table only from another table not from a query.
What you can do is attach a template table after the query and run the flow one time without the post load command. Make sure that the template table is in the same datastore as in the target table. Write the update query in post load like this -
update EMPLYR set EMPLYR.EMPLYR_PHN_NMBR_TXT = trmplatetable.EMPLYR_PHN_NMBR_TXT WHERE EMPLYR.EMPLYR_ID = templatetable.EMPLYR_ID
Hope this helps.
Arun