Question

I have the following query, the variable a works well if I don’t use an ORDER BY clause:

set @a:=0;

SELECT doc, @a as before, movement as mov, (@a:=@a+movement) as after, date 
FROM movements m
LEFT JOIN (
SELECT doc, 1 as tdoc, date
FROM invoices
UNION ALL
SELECT doc, 2 as tdoc, date
FROM nulled
) sub
ON m.doc=sub.doc and m.doc_type = sub.tdoc
WHERE m.product_id="XXXX"

so I get something like:

DOC BEFORE MOVEMENT AFTER DATE
006 0      10       10    2012-07-01
008 10     -3       7     2012-07-03
015 7      5        12    2012-06-20

But I want the movements to be ordered by date so I included ORDER BY date at the end of the query and I get:

DOC BEFORE MOVEMENT AFTER DATE
015 7      5        12    2012-06-20
006 0      10       10    2012-07-01
008 10     -3       7     2012-07-03

instead of what I want:

DOC BEFORE MOVEMENT AFTER   DATE
015 0       5        5      2012-06-20
006 5       10       15     2012-07-01
008 15      -3       12     2012-07-03

Is there a way to get this? the variable is being calculated and afterwards the results are ordered. Is there a way to force that the results are ordered first and then the variable is calculated?

Answer 1

Have you tried moving the ordering on subquery?

e.g.

set @a:=0;

SELECT doc, @a as before, mov, (@a:=@a+mov) as after, date  
FROM
(
    SELECT doc,  movement as mov, date 
    FROM movements m
    LEFT JOIN (
    SELECT doc, 1 as tdoc, date
    FROM invoices
    UNION ALL
    SELECT doc, 2 as tdoc, date
    FROM nulled
    ) sub
    ON m.doc=sub.doc and m.doc_type = sub.tdoc
    WHERE m.product_id="XXXX"
    order by date
) as x