将两列相加然后减去总和

Question

Here is my table.

pk |  transactionID
   |  description
   |  transactionDate
   |  transactionAmount
   |  accountRecieve
   |  accountSend

Those are my columns. I need to find the balance given an accountNumber through a query. To do this I have to SUM transactionAmount where accountSend = 127 and then SUM transactionAmount where accountRecieve = 127 and then subtract the first sum from the second sum and show it in one result.

I can explain it but I have no idea how to execute this in SQL. Can anyone please help.

Answer 1

One option uses conditional aggregation:

SELECT
    SUM(IIF(accountReceive = 127, transactionAmount, 0)) -
    SUM(IIF(accountSend = 127, transactionAMount, 0)) AS diff
FROM yourTable;

The idea is to just make a single pass over the entire table, summing the transaction amount using the two criteria.

Answer 2

You can also express this using switch :

SELECT SUM(SWITCH(accountReceive = 127, transactionAmount
                  accountSend = 127, - transactionAMount, 0,
                  1=1, 0
                 )
          ) AS diff
FROM yourTable;

This only uses one SUM() and is more analogous to using CASE in other databases.