删除所有未更改的条目（SQL）

Question

i got the following table player_teams which contains data like this

| id | p_id | year | t_id |
---------------------------
| 1  | 1    | 2001 | 1    |
| 2  | 1    | 2002 | 1    |
| 3  | 1    | 2003 | 1    |
| 4  | 1    | 2004 | 3    |
| 5  | 2    | 2001 | 1    |
| 6  | 2    | 2003 | 1    |
| 7  | 2    | 2004 | 2    |
| 8  | 2    | 2006 | 3    |
| 9  | 2    | 2007 | 1    |

fiddle now
fiddle result

now i want to delete every entry where the t_id didnt change to the next smaller entry in the year column. p_id has to be the same of course.

So in this Case id 2,3 and 6 should be deleted.

1: First entry of player (dont delete)
2: Nothing changed to the year 2001 (delete)
3: Nothing changed to the year 2002 (delete)
4: t_id changed to the year 2003 (dont delete)
5: First entry of player (dont delete)
6: Nothing changed to the year 2001 (2002 is missing) (delete)
7: t_id changed to the year 2003 (dont delete)
8: t_id changed to the year 2004 (2005 is missing) (dont delete)
9: t_id changed to the year 2006 (dont delete)

Note that all of the columns may miss specific values and are not sorted.

Goal is to only have the changes of the teams a player was in, not every year.

I dont know if its possible with sql or if i have to write a program which does it.

Thx

Answer 1

DELETE player_teams.*
FROM
  player_teams LEFT JOIN (SELECT p_id, MIN(year) As min_year
                          FROM player_teams
                          GROUP BY p_id, t_id) p
  ON player_teams.p_id = p.p_id AND player_teams.year=p.min_year
WHERE
  p.p_id IS NULL

Please see fiddle here . Or you can use this:

DELETE p1.*
FROM
  player_teams p1 INNER JOIN player_teams p2
  ON p1.p_id=p2.p_id
     AND p1.t_id = p2.t_id
     AND p1.year>p2.year

Fiddle is here .

Edit

If you need to keep row 9 because t_id changed to 1,2,3 and then changed back to 1, you need to use more complicated query like this:

DELETE
  player_teams.*
FROM
  player_teams INNER JOIN (
    SELECT p1.p_id, p1.year, MAX(p2.year) prev_year
    FROM
      player_teams p1 LEFT JOIN player_teams p2
      ON p1.p_id = p2.p_id AND p1.year>p2.year
    GROUP BY
      p1.p_id, p1.year) ny
  ON player_teams.p_id = ny.p_id AND
     player_teams.year = ny.year
  INNER JOIN player_teams pny
  ON ny.p_id = pny.p_id
     AND ny.prev_year=pny.year
     AND player_teams.t_id = pny.t_id

Fiddle is here .

Answer 2

Try this and see if it works.

DELETE FROM Table
WHERE id IN (SELECT id FROM Table t1 
              WHERE t1.id > id AND t1.p_id = p_id AND t_id = t1.t_id)