Question

我有以下用户表（不要问我为什么:)）

| id | cid | attr | text |   rdate    |
---------------------------------------
|  1 |  1  | name |  joe |    NULL    |
|  2 |  1  | date | NULL | 10.05.2014 |
|  3 |  1  | stat |   2  |    NULL    |
----------------------------------------
|  4 |  2  | name |  joe |    NULL    |
|  5 |  2  | date | NULL | 05.05.2014 |
|  6 |  2  | stat |   1  |    NULL    |
----------------------------------------
|  7 |  3  | name |  joe |    NULL    |
|  8 |  3  | date | NULL | 03.05.2014 |
|  9 |  3  | stat |   2  |    NULL    |

正如您所看到的，每个用户的属性（名称，日期，统计信息）都是表格中的一行。具有相同cid的属性属于同一用户。

我想删除所有引用属性日期在08.05.2014之前且其属性stat不是2的用户的条目。因此，在运行此查询后，该表将为：

| id | cid | attr | text |   rdate    |
---------------------------------------
|  1 |  1  | name |  joe |    NULL    |
|  2 |  1  | date | NULL | 10.05.2014 |
|  3 |  1  | stat |   2  |    NULL    |
----------------------------------------
|  7 |  3  | name |  joe |    NULL    |
|  8 |  3  | date |  joe | 03.05.2014 |
|  9 |  3  | stat |   2  |    NULL    |

有可能吗？这是同一个桌子上的内部联接吗？

Answer 1

按cid分组并使用having子句运行组功能以检查每个组中的要求

delete from your_table
where cid in
(
  select * from 
  (
    select cid
    from your_table
    group by cid
    having sum(attr = 'date' and `date` < '2014-05-08') > 0
    and sum(attr = 'stat' and `text` = 2) = 0
  ) tmp_tbl
)

在MySQL中，您无法从您选择的同一个表中删除。但是你可以使用上面例子中的另一个子查询来欺骗MySQL。

Answer 2

我会在delete语句中做一个相当简单的JOIN： -

DELETE a
FROM some_table a
INNER JOIN some_table b
ON a.cid = b.cid
INNER JOIN some_table c
ON a.cid = c.cid
WHERE b.attr = 'date' AND b.date < '2014-05-08'
AND c.attr = 'stat' AND c.text != '2'

Answer 3

您可以使用delete / join：

执行此操作

delete t
    from table t join
         (select cid
          from table t
          group by cid
          having max(case when attr = 'date' and date < '2014-05-08') > 0 and
                 max(case when attr = 'stat' and text <> '2') > 0
         ) s
         on t.cid = s.cid;

Answer 4

加入会做：

Delete from mytable where cid in (select cid from
    (select t1.cid FROM mytable t1 INNER JOIN mytable t2 ON t1.cid = t2.cid
         WHERE t1.attr = 'date' AND t1.rdate < '2014-05-08' 
                AND t2.attr = 'stat' AND t2.text != 2) as sq)

表上的多个内部联接，其中行表示数据属性

4 个答案: