Question

I have a MySQL table:

level      box
1           1
2           2
3           2
1           3
2           1
2           3
2           3
3           1

How can I get this table with MySQL query?

         box1     box2         box3
level1    1        0            1
level2    1        1            2
level3    1        1            0

I have a big table so request should be fast.
Thanks.

Answer 1

I believe this should do it, although there may be a more efficient method or one not requiring an aggregate.

Edit: Initially I misunderstood the requirement. Changed the MAX() aggregate to COUNT():

SELECT
  CONCAT('level', level) AS levelname,
  COUNT(CASE WHEN box = 1 THEN box ELSE NULL END) AS box1,
  COUNT(CASE WHEN box = 2 THEN box ELSE NULL END) AS box2,
  COUNT(CASE WHEN box = 3 THEN box ELSE NULL END) AS box3
FROM tbl
GROUP BY levelname

Another method using JOINs:

SELECT
  CONCAT('level', a.level) AS levelname,
  b1.num AS box1,
  b2.num AS box2,
  b3.num AS box3
FROM
  table a
  LEFT JOIN (SELECT level, COUNT(*) AS num FROM table WHERE box = 1) b1 ON a.level = b1.level
  LEFT JOIN (SELECT level, COUNT(*) AS num FROM table WHERE box = 2) b2 ON a.level = b2.level
  LEFT JOIN (SELECT level, COUNT(*) AS num FROM table WHERE box = 3) b3 ON a.level = b3.level