Calculate running balance

Question

I found below query to calculate running balance.

SELECT intId, varName, decAmt, charCrDr, 
       SUM(CASE WHEN charCrDr = 'c' THEN
               decAmt
           ELSE
              decAmt * -1
           END )
           OVER (PARTITION BY varName ORDER BY intId) As decTotal
FROM #Temp;

I would like to know what it means by else condition

Answer 1

这是执行SUM或DIFFERENCE操作的粗略方法：在这里，您要尝试找到decAmt的不同之处，如下所示：

decAmt(where charCrDr = 'c') - decAmt 

Answer 2

decAmt * -1将decAmt * -1的值乘以-1，这样，如果它为正数，它将变为负数；如果为负数，它将变为正数。

Answer 3

Actually it's about the Credit(Cr) and Debit(Dr). The running balance is:

sum of Credits - (sum of Debits)

So the decAmt for debit records (in the ELSE part, that is WHEN charCrDr != 'c' ) are multiplied by -1 to maintain the above formula.

Good Luck.