Question

我有一个带有表Table1的Access DB，该表包含以下信息：

ADDRESS_ID | CATEGORY_ID
1          | 12
2          | 41
2          | 66
3          | 41
4          | 41
4          | 66

每个ADDRESS_ID都属于一个专用客户（唯一分配）。

我需要创建一个SQL查询，该查询仅返回表中那些ADDRESS_ID恰好具有一个专用条目的行，例如如果我的过滤条件是“返回CATEGORY_ID = 41”，则预期结果是：

ADDRESS_ID | CATEGORY_ID
3          | 41

或者如果它是“ Return CATEGORY_ID = 66”，则结果为空表。

如何在不通过脚本执行后处理的情况下实现查询？

Answer 1

我将使用group by和having：

select address_id
from table1
group by address_id
having min(category_id) = max(category_id) and
       min(category_id) = 41;

如果需要，可以将41 as category_id添加到select，但是您已经知道了。

如果表中没有重复的对，则也可以将其表达为：

select address_id
from table1
group by address_id
having count(*) = 1 and
       min(category_id) = 41;

Answer 2

使用build.gradle和count()：

having

Answer 3

我会使用NOT EXISTS：

select t.*
from table as t
where CATEGORY_ID = 66 and
      not exists (select 1 
                  from table as t1 
                  where t1.ADDRESS_ID = t.ADDRESS_ID and t1.CATEGORY_ID <> t.CATEGORY_ID
                 );

Answer 4

此查询：

select address_id, max(category_id) category_id
from tablename
group by address_id
having min(category_id) = max(category_id)

返回：

仅表中ADDRESS_ID恰好为1的那些行专用条目

现在，您可以对其应用任何过滤器并获得所需的结果：

select t.* from (
    select address_id, max(category_id) category_id
    from tablename
    group by address_id
    having min(category_id) = max(category_id)
) t
where t.category_id = 41

按多个条目过滤查询结果

4 个答案: