Нямате нужда от 4 различни заявки, просто избройте всичките си дялове в заявката:
set linesize 1000
set feedback off
set underline off
spool C:\Users\file.csv replace
SELECT cust_no FROM customer PARTITION (customer_PR1, customer_PR2, customer_PR3, customer_PR4)
WHERE city='ba' AND first_name='john'
AND salary=1000;
spool off;