Laravel group by and SUM - mysql

Question

Having trouble getting my head around this one, it likely doesn't help I don't have any SQL 'group by' experience.
I have a table that has a transaction_type column and an amount column. Basically I am trying to use SQL/Eloquent to get the following in a single query (if possible, I know this isn't sql):
add = SUM(amount) where transaction_type == 1
delete = SUM(amount) WHERE transaction_type == 2
return from MySQL: add-delete
I'm assuming this would be done using groupby, but despite my best efforts I haven't be able to find a solution by reading the sql documentation.
I think I have got it using plain SQL, but how would I convert this to Eloquent:
SELECT `transaction_type`, SUM(`amount`) FROM `credit_logs` WHERE `to_group_id` = '1'

Answer 1

I can't help you with eloquent, but your query should be something like this:
SELECT
SUM(CASE WHEN transaction_type = 1 THEN amount ELSE NULL END)
-
SUM(CASE WHEN transaction_type = 2 THEN amount ELSE NULL END)
FROM credit_logs
WHERE to_group_id = 1;
or for all id's you wish to group by:
SELECT
SUM(CASE WHEN transaction_type = 1 THEN amount ELSE NULL END)
-
SUM(CASE WHEN transaction_type = 2 THEN amount ELSE NULL END)
FROM credit_logs
GROUP BY to_group_id;
Easiest would be, if you'd find a way to just execute a query with eloquent. Never understood why someone wants to transform a nice readable query into some "improved" syntax of a framework.