FROM clauses are not allowed in expressions in PSQuery

Hi,

I have a query with 2 sqls .

My requirement is if the 1st sql reurns rows then query should not include the values from bottom union.

Currently I am trying with 2 sqls with case starement. This is working fine in the back end (Oracle).

When I am trying in PS query with expression I am getting the below error.

Sample SQL:

 

  select case when  COUNTER > 0   then oprid

            else (select oprid from sysadm.PS_TABLE2  WHERE COUNTER > 0  and emplid = '123455' )

       end

from  sysadm.PS_TABLE2

WHERE emplid = '123455'

Error: FROM clauses are not allowed in expressions in PSQuery

If the top sql returns values then query should have values from Top sql only.