Well you can try using database xpath function in assign activity and get the data instead of database adapter.

XPath Extension Functions

Regards,

Anshul

Say your complete query looks like this -

select SUBJECT_NAME from RELATION

            where PID_GID_SSID IN (select PARTY_KEY from  xref WHERE row_id='123')

1). In assign activity, write out the query part which comes after where clause and assign to variable query

(select PARTY_KEY from  xref WHERE row_id='123') , replace the value of row_id from input value in assign.

2. Now open DB adapter and pass the rest of query as input -

select SUBJECT_NAME from RELATION

            where PID_GID_SSID IN #query