How to SQL SUM with condition

Question

I have a transaction table and want to calculate based on the type of transaction. How to?

Table:

id | amount | type
--------------------
01 | 230    | IncomingTransfer
02 | 100    | OutcomingTransfer
03 | 20     | IncomingTransfer

Logic:

SELECT SUM(amount)
IF IncomingTransfer
    + 230
    + 20
ELSE IF OutcomingTransfer
    - 100

Total amount: +150

Answer 1

AS simple as my sqlfiddle shows:

select
sum(CASE WHEN type = 'IncomingTransfer' THEN amount ELSE -amount END) as totalsum
from t;