Question

I have table with positions

tbl_positions
   id position
    1 Driver
    2 Lobby
    3 Support
    4 Constructor 

and in other table i have users

EDIT:

   tbl_workers
      id   name   position position2 status
       1   John   2        3         4
       2   Mike   3        2         2
       3   Kate   2        0         3
       4   Andy   1        0         0

i do request of positions

SELECT p.id, 
    p.position, 
    SUM(CASE w.Status WHEN 2 THEN 1 ELSE 0 END)  AS booked,
    SUM(CASE w.Status WHEN 3 THEN 1 ELSE 0 END)  AS placed
  FROM  tbl_positions AS p LEFT JOIN tbl_workers AS w 
      ON w.position=p.id
GROUP BY p.id, p.position

I need output like this in single query.

Position    booked placed
Driver        0       0
Lobby         1       2
Support       0       2
Constructor   0       0

I need to evalate both field positon1 and position2 instead of one. I think its easy to modify it but i cannot find the right solution please help.

EDIT : Added status 4

Answer 1

Instead of joining to tbl_workers you could join to its unpivoted variation where position and position2 would be in the same column but in different rows.

Here’s how the unpivoting might look like:

SELECT
  w.id,
  w.name,
  CASE x.pos WHEN 1 THEN w.position ELSE w.position2 END AS position,
  w.status
FROM tbl_workers AS w
  CROSS JOIN (SELECT 1 AS pos UNION ALL SELECT 2) AS x

Here’s the entire query, which is basically your original query with the above query substituting for the tbl_workers table:

SELECT p.id, 
  p.position, 
  SUM(CASE w.Status WHEN 2 THEN 1 ELSE 0 END)  AS booked,
  SUM(CASE w.Status WHEN 3 THEN 1 ELSE 0 END)  AS placed
FROM tbl_positions AS p
  LEFT JOIN (
    SELECT
      w.id,
      w.name,
      CASE x.pos WHEN 1 THEN w.position ELSE w.position2 END AS position,
      w.status
    FROM tbl_workers AS w
      CROSS JOIN (SELECT 1 AS pos UNION ALL SELECT 2) AS x
  ) AS w 
  ON w.position=p.id
GROUP BY p.id, p.position

---

UPDATE

This is a modified script according to additional request in comments:

SELECT p.id, 
  p.position, 
  SUM(CASE w.Status WHEN 2 THEN 1 ELSE 0 END)  AS booked,
  SUM(CASE w.Status WHEN 3 THEN 1 ELSE 0 END)  AS placed
FROM tbl_positions AS p
  LEFT JOIN (
    SELECT
      w.id,
      w.name,
      CASE x.pos WHEN 1 THEN w.position ELSE w.position2 END AS position,
      CASE w.status
        WHEN 4 THEN CASE x.pos WHEN 1 THEN 3 ELSE 2 END
        ELSE w.status
      END AS status
    FROM tbl_workers AS w
      CROSS JOIN (SELECT 1 AS pos UNION ALL SELECT 2) AS x
  ) AS w 
  ON w.position=p.id
GROUP BY p.id, p.position

The idea is to substitute the 4 status in the subselect with 3 or 2 depending on whether we are currently to pull position or position2 as the unified position. The outer select keeps using the same logic as before.