SELECT Table From Select Other Table

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SELECT ID From Table2 Where Select ID From Table1

Posted 26-Jan-15 6:13am

Member 11057420

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[no name] 26-Jan-15 12:15pm

SELECT TABLE2.ID (and others you need) FROM TABLE2 LEFT JOIN TABLE1 ON TABLE1.ID = TABLE2.ID WHERE NOT TABLE1.ID IS NULL.

Member 11057420 26-Jan-15 13:08pm

thx you, this solved my problem

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Simon_Whale · Answer 1 · 2015-01-26T06:24:00

Your table examples and description don't give much to go on as the relationship of the tables is not known. I can only guess on the ID columns but I am unsure.

If you are looking at joining the information in the 2 tables on matching information I would start with inner join[^].

you can also look up information on outer joins, I would Google on "TSQL left outer join" if you want to show information that is in the left table but not the right table

P.S I have made an assumption that you are looking at SQL Server, If I am wrong please let know and I'll update my answer.

Abhinav S · Answer 2 · 2015-01-26T07:26:00

Solution 2

You can use the IN clause.
select id from table2 where id IN (select id from table1 where <<some condition>>)

The same query can be written as a JOIN. You can try that out yourself.

Posted 26-Jan-15 7:26am

Abhinav S

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[no name] 26-Jan-15 14:03pm

Or also EXISTS but IN and EXISTS are usually not that performant, especially on tables with a lot of records. This is just by experience, don't ask me why it is like that ;)

The above is true at least for EXISTS, IN I have to check again, I think a light goes on in my brain....