I need to add the value of a column in SQL, so it looks like this:
SELECT SUM(qtdsaco) FROM armazem
This code works. Now I need to add the value of the other table, it looks like this:
SELECT SUM(qtdsaco) FROM armazem2
So I had to take the result of the two and subtract. How do I?
You will have to see which table comes first and do this by throwing the value into a total :
SELECT (SUM(qtdsaco) - (SELECT SUM(qtdsaco) FROM armazem2)) total FROM armazem
The SELECT serves to select information in any way. It does not even need to be from the database. It can select data if SQL subexpression, including other% s of% s. Then you can do each of them as subexpression and the subtraction of the two in SELECT principal.
SELECT (SELECT SUM(qtdsaco) FROM armazem) - (SELECT SUM(qtdsaco) FROM armazem2)
See running SQLFiddle .
Obviously you can get the same result with variations of SQL expression. I find this more appropriate because it is simple and clearly demonstrates intent. If I had other requirements I would opt for another way. I followed what the question asked ipsis litteris .
Based on in this other answer of mine , I would do so:
SELECT a.c - b.d AS qtdsaco
FROM (SELECT SUM(qtdsaco) AS c FROM armazem) a,
(SELECT SUM(qtdsaco) AS d FROM armazem2) b
Make use of subselects :
select (SELECT SUM(qtdsaco) FROM armazem) - (SELECT SUM(qtdsaco) FROM armazem2)
You can do a JOIN as follows.
declare @armazem table(qtdsaco int)
declare @armazem2 table( qtdsaco int)
insert into @armazem values(112),(3),(432),(22),(1),(5),(4),(3),(2)
insert into @armazem2 values(1),(2),(3),(4),(6),(5),(4),(3),(2)
select SUM(a1.qtdsaco) - SUM(a2.qtdsaco) total
from @armazem a1
join @armazem2 a2 on 1 = 1
Obs; as the database was not specified, this was done in sql server.