Question

我有一个这样的数据表：

-------------+-------------+-------
| foo_date   | description | flag |
-------------+-------------+-------
| 2014-01-01 | asdf 123    | 1    |
-------------+-------------+-------
| 2014-01-01 | FOO         | 1    |
-------------+-------------+-------
| 2014-01-02 | asdf 456    | 1    |
-------------+-------------+-------

我试图将任何行的标志设置为0，其中描述不是＆＃39; t＆＃34; FOO＆＃34;并且在同一天有一排是＆＃34; FOO＆＃34;。因此，在此示例数据集中，第一行将获得flag = 0，因为同一日期存在FOO，但第三行不会因为该日期没有匹配的FOO。这就是我提出的有效的方法，但它并不是最有效的方法。

UPDATE
  foo_table t1
JOIN
(
  SELECT 
    * 
  FROM 
    foo_table
  WHERE
    (foo_date) IN 
    (
      SELECT 
        foo_date
      FROM 
        foo_table 
      WHERE 
        description LIKE 'FOO%'
    )
    AND description NOT LIKE 'FOO%'
) AS t2
ON
(
  t1.foo_date = t2.foo_date
  AND t1.description = t2.description
)
SET
  t1.flag = 0

Answer 1

update t1
set t1.flag = 0
from foo_table t1
where     t1.description <> 'FOO'
      and exists (select * 
                  from foo_table t2 
                  where     t2.foo_date=t1.foo_date 
                        and t2.description = 'FOO')

Answer 2

根据您的数据，这可能会更有效：

update t1
set t1.flag = 0
from foo_table t1
where isnull(t1.description,'') <> 'FOO'
and t1.foo_date in (select t2.foo_date 
                  from foo_table t2 
                  where t2.description = 'FOO')

SQL更新使用相同的表子查询结果

2 个答案: