1. Write distinct statement in the field where table name is entered, but this has a limitation to the number of characters that can be entered. so if query is long then you cannot make use of this feature.

(select distinct col_value from table a) b

 

Now b becomes the new table

 

use b.col_value

2. Create a view based on your query and use that view in the value set.

3. Write your query in such a way that it gives you a distinct value. You can make use of ROWID to meet the requirement.

For Example:-----------------SELECT ooh.order_numberFROM oe_order_lines_all ool, oe_order_headers_all oohWHERE ool.header_id = ooh.header_idAND ool.ROWID = (SELECT MAX(ROWID)FROM oe_order_lines_all oo11WHERE oo11.header_id = ooh.header_id);

allow parent values check pox

See MOS Doc 1069797.6 - DFF: DISTINCT CLAUSE DOES NOT WORK IN VALIDATION

Please see (Note: 356986.1 - Receiving ORA-00936 Error When Using Distinct Clause In Value Set).