How to find the difference of sums by condition?

Question

SQL Server

How to find the difference of sums by condition? More details: there are two columns in one type of document, in the second its sum and you need to subtract the first sum of documents by type (Data grouped) from the second. Example:

select (sum(amount) and idoperation = 1) - (sum(amount) and idoperation = 2)
from journal group by idoperation

But executing such a query reports a syntax error.
If it is simpler, then subtract the value of the subsequent ones from the first value

Answer 1

Everything can be easier:

SELECT 
SUM(ammount * (CASE WHEN idoperation = 1 THEN 1 ELSE -1 END)) AS result
FROM journal
;

SQL SUM fiddle