Question

I have table like this:

+----+---------+---------+--------+
| id | value_x | created | amount |
+----+---------+---------+--------+

value_x is set of six strings, lets say “one”, “two”, “three”, etc.
I need to create report like this:

+--------------+-------------------------+-------------------+----------------------+
| day_of_month |          "one"          |      "two"        |          [etc.]      |
+--------------+-------------------------+-------------------+----------------------+
|  01-01-2011  | "sum(amount) where value_x = colum name" for this specific day     |
+--------------+-------------------------+-------------------+----------------------+

Most obvious solution is:

SELECT SUM(amount), DATE(created) FROM `table_name` WHERE value_x=$some_variable GROUP BY DATE(created)

And loop this query six times with another value for $some_variable in every iteration, but I’m courious if is it possible to do this in single query?

Answer 1

What you’re asking is called a “pivot table” and is typically achieved as below. The idea is for each potential value of value_x you either produce a 1 or 0 per row and sum 1’s and 0’s to get the sum for each value.

SELECT
  DATE(created),
  SUM(CASE WHEN value_x = 'one' THEN SUM(amount) ELSE 0 END) AS 'one',
  SUM(CASE WHEN value_x = 'one' THEN SUM(amount) ELSE 0 END) AS 'two',
  SUM(CASE WHEN value_x = 'one' THEN SUM(amount) ELSE 0 END) AS 'three',
  etc...
FROM table_name
GROUP BY YEAR(created), MONTH(created), DAY(created)