[英]MS Access: Compare 2 tables with duplicates
I have two tables which look like this: 我有两个看起来像这样的表:
T1: T1:
ID | Date | Hour
T2: T2:
ID | Date | Hour
I basically need to join these tables when their IDs, dates, and hours match. 当它们的ID,日期和小时数匹配时,我基本上需要加入这些表。 However, I only want to return the results from table 1 that do not match up with the results in table 2.
但是,我只想返回表1中的结果与表2中的结果不匹配的结果。
I know this seems simple, but where I'm stuck is the fact that there are multiple rows in table 1 that match up with table 2 (there are multiple intervals for any given hour). 我知道这似乎很简单,但我遇到的问题是表1中有多行与表2匹配(任何给定小时都有多个间隔)。 I need to return all of these intervals so long as they do not fall within the same hour period in table 2.
我需要返回所有这些间隔,只要它们不在表2的同一小时内即可。
Example data: 示例数据:
T1: T1:
1 | 1/1/2011 | 1
1 | 1/1/2011 | 1
1 | 1/1/2011 | 1
1 | 1/1/2011 | 2
T2: T2:
1 | 1/1/2011 | 1
1 | 1/1/2011 | 1
My expected result set for this would be the last 2 rows from T1. 我的预期结果集是T1的最后2行。 Can anyone point me on the right track?.
谁能指出我在正确的道路上?
I think you just want not exists
: 我想你只是想
not exists
:
select t1.*
from t1
where not exists (select 1
from t2
where t2.id = t1.id and t2.date = t1.date and t2.hour = t1.hour
);
EDIT: 编辑:
I misread the question. 我看错了问题。 This is very hard to do in MS Access.
在MS Access中很难做到这一点。 But, you can come close.
但是,您可以接近。 The following returns the distinct rows in table 1 that do not have equivalent numbers in table 2:
以下代码返回表1中不同的行,这些行在表2中没有相同的数字:
select t1.id, t1.date, t1.hour, (t1.cnt - t2.cnt)
from (select id, date, hour, count(*) as cnt
from t1
group by id, date, hour
) t1 left join
(select id, date, hour, count(*) as cnt
from t2
group by id, date, hour
) t2 left join
on t2.id = t1.id and t2.date = t1.date and t2.hour = t1.hour
where t2.cnt < t1.cnt;
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