To calculate the variance percentage

Question

In below given query , i want to calculate the variance between Forecast and sale.
Here
FRCST - Forecast
SALE - Sale
FRCST-sale - Difference between forecast and sale
Now i want to display one more column i.e Variance
I need a statement to caluclate the DIFF / FRCST. The result should be displayed according the conditions :
1) If Forecast is Zero, and Sale is Zero - then result should be No Forecast and Sale for the item
2) If Forecast is Zero, and sale is not Zero, then Sale against Nil Forecast
3) If Sale is Zero and Forecast is not Zero then No sale against Forecast
4) If difference between Forecast and Sale is zero (Both are non zero numbers) then No Variance
5) If Forecat and Sale difference is not Zero then DIFF / FRCST
The problem arise when the FRCST is Zero and Sale is non zero then divide by zero occurs
Kindly guide me on this..
SELECT ITEM_NAME, NVL(FRCST,0) FRCST, NVL(SALE,0) SALE, NVL((FRCST-SALE),0) DIFF
FROM
SELECT DISTINCT ITEM_NAME
FROM OM_ITEM
WHERE ITEM_CODE LIKE 'F%'
AND ITEM_FRZ_FLAG_NUM<>1
SELECT FYEAR, FMNTH, FITEM_NAME,FRCST
FROM FORECAST
WHERE FYEAR||'-'||FMNTH = :YM
SELECT SYEAR, SMNTH, SITEM_NAME, SALE
FROM SALE
WHERE SYEAR||'-'||SMNTH = :YM
WHERE ITEM_NAME = FITEM_NAME(+)
AND ITEM_NAME = SITEM_NAME(+)
ORDER BY 1

Answer 1

I had changed the query as given below . Its giving me result, but how could i convert the case statement into decode. Is there any simple way for this:
SELECT
ITEM_NAME, FRCST, SALE, DIFF,
(CASE
WHEN FRCST = 0 AND SALE = 0 THEN 'No transaction '
WHEN FRCST = 0 AND SALE <>0 THEN 'Sale against Nil Forecast'
WHEN FRCST<> 0 AND SALE = 0 THEN 'No Sale against Forecast'
WHEN FRCST<>0 AND SALE<>0 AND DIFF=0 THEN 'No Variance'
ELSE TO_CHAR(ROUND((DIFF/FRCST),2))||'%'
END)VARIANCE
FROM
SELECT ITEM_NAME, NVL(FRCST,0) FRCST, NVL(SALE,0) SALE, NVL((FRCST-SALE),0) DIFF
FROM
( SELECT DISTINCT ITEM_NAME FROM OM_ITEM
WHERE ITEM_CODE LIKE 'F%'
AND ITEM_FRZ_FLAG_NUM<>1
( SELECT FYEAR, FMNTH, FITEM_NAME, FRCST
FROM FORECAST
WHERE FYEAR||'-'||FMNTH = :YM
( SELECT SYEAR, SMNTH, SITEM_NAME, SALE FROM SALE
WHERE SYEAR||'-'||SMNTH = :YM
WHERE ITEM_NAME = FITEM_NAME(+) AND ITEM_NAME = SITEM_NAME(+)
ORDER BY 1
)