Question

我在一个名为ELEM的表中有一个包含数万个元素的数据库，我想删除其中一些元素。

我无法使用简单的命令（DELETE .. FROM ... WHERE ...），因为无法直接定位它们。

select * from ELEM;

+----+--------+
| id |  text  |
+----+--------+
|  1 | text1  |
|  2 | text2  |

但我可以找到他们的身份：

select * from connect where list_id=3

+-----+-----------+-----------+-----------+
| id  |  list_id  | elem_1_id | elem_2_id |
+-----+-----------+-----------+-----------+
| 378 |         3 |      2568 |      2569 |
| 379 |         3 |      2568 |      2570 |
| 380 |         3 |      2571 |      2572 |

如何使用此结果中的变量elem_1_id和elem_2_id在ELEM表中删除？

Answer 1

假设您要从“ELEM”中删除＆＃39;基于＆＃39; connect＆＃39;中的elem_1_id的表格你可以使用表格＆＃39; IN＆＃39;子查询：

DELETE FROM ELEM WHERE id IN (
  SELECT elem_1_id FROM connect WHERE list_id = 3
)

如果你想根据elem_1_id或elem_2_id删除，你可以做两个子查询，例如：

DELETE FROM ELEM WHERE id IN (
  SELECT elem_1_id FROM connect WHERE list_id = 3
) OR id IN (
  SELECT elem_2_id FROM connect WHERE list_id = 3
)

Answer 2

我做这样的事情：

delete e.* from elem as e
inner join connect as c on c.elem_1_id = e.id
where c.list_id = 3;

delete e.* from elem as e
inner join connect as c on c.elem_2_id = e.id
where c.list_id = 3;

在mysql表中定位和删除元素

2 个答案: