我有两个看起来像这样的表:
I have two tables which look like this:
T1: ID | Date | Hour | Interval T2: ID | Date | Hour我基本上需要在它们的 ID、日期和时间匹配时加入这些表.但是,我只想返回表 1 中与表 2 中的结果不匹配的结果.
I basically need to join these tables when their IDs, dates, and hours match. However, I only want to return the results from table 1 that do not match up with the results in table 2.
我知道这看起来很简单,但我遇到的问题是表 1 中有多行与表 2 匹配(任何给定的小时都有多个间隔).我需要返回所有这些间隔,只要它们不在表 2 中的同一小时内.
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). I need to return all of these intervals so long as they do not fall within the same hour period in table 2.
示例数据:
T1: 1 | 1/1/2011 | 1 | 1 1 | 1/1/2011 | 1 | 2 1 | 1/1/2011 | 2 | 1 1 | 1/1/2011 | 2 | 2 T2: 1 | 1/1/2011 | 1我的预期结果集将是 T1 的最后两行.任何人都可以指出我在正确的轨道上吗?
My expected result set for this would be the last two rows from T1. Can anyone point me on the right track?
推荐答案 SELECT T1.* FROM T1 WHERE NOT EXISTS(SELECT NULL FROM T2 WHERE T1.ID = T2.ID AND T1.Date = T2.Date AND T1.Hour = T2.Hour)也可以使用 LEFT JOIN 来完成:
It could also be done with a LEFT JOIN:
SELECT T1.* FROM T1 LEFT JOIN T2 ON T1.ID = T2.ID AND T1.Date = T2.Date AND T1.Hour = T2.Hour WHERE T2.ID IS NULL更多推荐
如何连接两个表但只返回不匹配的行?
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