如果一列中的值存在于另一列中，则过滤行 [英] Filter rows if value in one column exists in another column

问题描述

我在Postgres 11中有下表:

I have following table in Postgres 11:

col1   col2            col3               col4   
1      trial_1         ag-270              ag
2      trial_2         ag                  ag
3      trial_3         methotexate (mtx)   mtx
4      trial_4         mtx                 mtx
5      trial_5         hep-nor-b           nor-b

我想在col3列中搜索col4的每个值.如果col3中存在col4中的值，我想保留这些行，否则应将该行排除在外.

I would like to search each value of col4 throughout the column col3. If the value in col4 exists in col3, I would like to keep the rows else the row should be excluded.

所需的输出是:

col1   col2            col3               col4   
1      trial_1         ag-270              ag
2      trial_2         ag                  ag
3      trial_3         methotexate (mtx)   mtx
4      trial_4         mtx                 mtx

我无法对此进行任何尝试，因为我还无法找到解决方案.

I could not try anything on this as I am unable to find a solution to this yet.

推荐答案

这可以作为内部联接来完成:

This can be done as an inner join:

select distinct t.col1, t.col2, t.col3, t,col4
from T t inner join T t2 on t2.col3 = t.col4 

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