Nested Query in ORACLE

[chrisrlong]

Never go into a table more than once if you don't have to.

SELECT
   WAREHOUSE,
   COUNT(*)
      AS NUM_LINES, 
   SUM(
      CASE
         WHEN
            B.Q_OH   =  0
         THEN
            1
      END
      )
      AS ZERO_BAL
FROM
   INVENTORY
WHERE
   WAREHOUSE  =  :WAREHOUSE AND
   Q_RO       >  0 
GROUP BY
   WAREHOUSE   ;

- Chris