MySQL sum() on different group bys - mysql

Question

Ok, I have a query over two tables. I need to get two sums. I do a group by so the sum() works correctly.
SELECT sum(a.x), sum(b.y) FROM a,b GROUP BY a.n where a.n=b.m
So far this works well, but the problem is i need to group them differently for the second sum (sum(b.y)), than for the first sum (sum(a.x)).
The real query is somewhat more complex but this is my main problem.
This is what i actually try to select sum(stock.amount) - if( sold.amount IS NULL , 0, sum( sold.amount ) )
How can I solve that in one query?

Answer 1

since you are not writing down the tables I am gonna make a wild guess and assume the tables are like :
stock : id, item_id, amount
sold : id, item_id, amount
then again I assume that you need the stock_in_total, sold_total, left_total counts
SELECT
stock_sums.item_id,
stock_sums.st_sum as stock_in_total,
COALESCE(sold_sums.so_sum,0) as sold_total,
(stock_sums.st_sum - COALESCE(sold_sums.so_sum,0)) as left_total
FROM (
SELECT stock.item_id as item_id, SUM(stock.amount) as st_sum
FROM stock
GROUP BY item_id
) as stock_sums
LEFT JOIN (
SELECT sold.item_id as item_id, SUM(sold.amount) as so_sum
FROM sold
GROUP by item_id
) as sold_sums ON stock_sums.item_id = sold_sums.item_id
I hope this would help.

Answer 2

Here is how I would do it. I assume that Stock is the main table, with an ID and an amount, and that Sold maps to Stock via an ID value, and has zero to many records for each Stock item.
SELECT Q1.id, Q1.Total1, Q2.Total2
, Q1.Total1 - COALESCE(Q2.Total2,0) as Outstanding
FROM (
SELECT id, SUM(amount) as Total1
FROM Stock GROUP BY id
) as Q1
LEFT OUTER JOIN (
SELECT id, SUM(Amount) as Total2
FROM Sold GROUP BY id
) as Q2
ON Q2.id = Q1.id
Note that simply formatting your SQL into a clean way forces you to break it into logical parts and will often reveal exactly what is wrong with the query.
The example above also handles correctly the cases where there is not match in the Sold table.
Cheers,
Daniel
(Code Assumptions)
DROP TABLE Stock
CREATE TABLE Stock (
id integer
, amount decimal(10,2)
)
INSERT INTO Stock (id, amount ) VALUES ( 1, 10.1);
INSERT INTO Stock (id, amount ) VALUES ( 2, 20.2);
INSERT INTO Stock (id, amount ) VALUES ( 3, 30.3);
SELECT * FROM STOCK
DROP TABLE Sold
CREATE TABLE Sold (
id integer
, amount decimal(10,2)
)
INSERT INTO Sold (id, amount ) VALUES ( 1, 1.1);
INSERT INTO Sold (id, amount ) VALUES ( 1, 2.2);
INSERT INTO Sold (id, amount ) VALUES ( 1, 3.3);
INSERT INTO Sold (id, amount ) VALUES ( 2, 2.22);
SELECT * FROM Sold
SELECT Q1.id, Q1.Total1, Q2.Total2
, Q1.Total1 - COALESCE(Q2.Total2,0) as Outstanding
FROM (
SELECT id, SUM(amount) as Total1
FROM Stock GROUP BY id
) as Q1
LEFT OUTER JOIN (
SELECT id, SUM(Amount) as Total2
FROM Sold GROUP BY id
) as Q2
ON Q2.id = Q1.id
Results:
id Total1 Total2 Outstanding
1 10.10 6.60 3.50
2 20.20 2.22 17.98
3 30.30 30.30

Answer 3

REVISION
It sounds like you want the total amount of stock you have as one count for each different stock. Then you want how much stock you have left for each stock based on what has been sold. Correct?
If so check this out:
select stock, sum(a.x) as sharesBeforeSale, (sum(a.x) - sum(b.y)) as sharesAfterSale
FROM db.table1 a, db.table2 b
WHERE a.UNIQUEID = b.UNIQUEID AND b.y IS NOT NULL
GROUP BY a.UNIQUEID;
Does that accomplish what you are looking to do?
stock sharesBeforeSale sharesAfterSale
duk 100 25
orc 101 101
yrc 54 41
Enjoy!
Sample tables
db.table1 (stock owned):
UNIQUEID x stock
1 100 duk
2 101 orc
3 54 yrc
db.table2 (stock sold):
UNIQUEID y
1 75
2 0
3 13