Question

我理解标题可能有点模糊，所以我会尝试用一个小例子来解释我想做什么。

我有一张叫做学生的桌子。我想从我的表中多次删除学生的所有记录。彼得和所有的记录都是如此。亚伦必须被删除。

SELECT student, count(student) AS cnt FROM `testtable` GROUP BY `student` HAVING cnt > 1

我还想删除数学为8的所有记录。

SELECT id FROM `testtable` WHERE mathematics = 8

但是我如何从这些选择查询中获取删除查询？甚至可以将2 ??

组合起来

表：学生

id   mathematics   biology   student 
--   -----------   -------   -------
0    6             8         Peter
1    6             8         Peter
2    3             9         Aaron
3    8             9         Alicia
4    1             4         Peter
5    7             7         Aaron
6    6             5         Rachel

Answer 1

感谢Uueerdo，他向我指出了这个方向，我让它发挥作用。

DELETE FROM testtable 
WHERE mathematics =8 
OR student IN (
    SELECT stu
    FROM (
        SELECT student AS stu
        FROM `testtable`
        GROUP BY `student`
        HAVING count( 1 ) >1
    )tmp
)

Answer 2

这样的东西可能会起作用（我说可能因为MySQL可能不喜欢引用子查询中的DELETE表）：

DELETE FROM testable 
WHERE mathematics = 8 
OR student IN (
   SELECT student 
   FROM `testtable` 
   GROUP BY `student` 
   HAVING count(1) > 1
)
;

这种方式更长，但几乎可以保证：

CREATE TEMPORARY TABLE `t` 
  SELECT student, count(student) AS cnt 
  FROM `testtable` 
  GROUP BY `student` 
  HAVING cnt > 1
;
DELETE FROM testable 
WHERE mathematics = 8 
OR student IN ( SELECT student FROM `t` )
;
DROP TEMPORARY TABLE `t`;

Answer 3

DELETE x
  FROM my_table x 
  JOIN my_table y 
    ON (y.student = x.student AND y.id <> x.id) 
    OR (y.id = x.id AND y.mathematics = 8);

1从2个选择查询中删除查询

3 个答案: