Question

I have a table with a couple of thousand rows: from this I need to extract a total for column WTE for each value in column band, including those where the total is 0. I also need each total to be in a column of its own, so that I can easily update a summary table.

The code I have at present returns the values from the relevant rows:

SELECT 
   IF(band="E",WTE,0) AS `Band6_WTE`
FROM  `orthoptists` AS o
LEFT JOIN `instances` AS i
ON o.instance_FK = i.id
WHERE i.region = 14

But when I add SUM(), the return is incorrect (zero, when it should be several thousands):

SELECT 
   IF(band="E",SUM(WTE),0) AS `Band6_WTE`
FROM  `orthoptists` AS o
LEFT JOIN `instances` AS i
ON o.instance_FK = i.id
WHERE i.region = 14

I have looked at http://en.wikibooks.org/wiki/MySQL/Pivot_table, but I do not understand how that approach should be applied to my problem.

What should I do?

Answer 1

you must sum if:

SELECT
    SUM(IF(band="E",WTE,0)) AS `Band6_WTE`
FROM  `orthoptists` AS o
LEFT JOIN `instances` AS i
ON o.instance_FK = i.id
WHERE i.region = 14