Question : Query Help

SELECT BALANCEAMOUNT FROM MONTHLYBILL
WHERE TRANSMONTH='MAY-2010'
AND MEMBERACCNO='B-100'

SELECT RECEIPTAMOUNT FROM MONTHLYBILL
WHERE TRANSMONTH='JUNE-2010'
AND MEMBERACCNO='B-100'

SELECT RECEIPTAMOUNT FROM MONTHLYBILL
WHERE TRANSMONTH='JULY-2010'
AND MEMBERACCNO='B-100'

Hi Need help to rewrite the above query to return result as follows
The ouput should be balanceamount (which is from monthy of may 2010) - sum(receiptamount) (which is from month of june july)

Answer : Query Help

SELECT
      SUM(CASE WHEN TRANSMONTH='MAY-2010' THEN BALANCEAMOUNT END)
      -SUM(CASE WHEN TRANSMONTH<>'MAY-2010' THEN RECEIPTAMOUNT END)
FROM MONTHLYBILL A
WHERE TRANSMONTH IN ('MAY-2010','JUNE-2010','JULY-2010')
  AND MEMBERACCNO='B-100'