MySQL ORDER BY Another table's column names

Question

I have one table with items for an order that looks like this:

Product | Color | Size | Size Range ID (from a different, joined table)
-----------------------------------------------------------------------
Shirt   | Blue  |  L   |   1
Shirt   | Blue  |  M   |   1
Shirt   | Blue  |  S   |   1

Note that the sizes are sorted in alphabetical order in the table above.

I also have a size ranges table that looks like this:

id | size_01 | size_02 | size_03
--------------------------------
 1 |    S    |   M     |   L  

How can I force the items on the first table to ORDER BY the position of the size in the second table?

Answer 1

You can use join to combine the tables and then field() to get the position in the column list:

select i.*
from items i left outer join
     SizeRange sr
     on i.SizeRangeId = sr.SizeRangeId
order by field(i.Size, sr.size_01, sr.size_02, sr.size_03)

Answer 2

SELECT
  MAX(CASE Size WHEN 'S' THEN Size ELSE '' END) AS 'size_01',
  MAX(CASE Size WHEN 'L' THEN Size ELSE '' END) AS 'size_02',
  MAX(CASE Size WHEN 'M' THEN Size ELSE '' END) AS 'size_03'
FROM Test
GROUP BY Product