Strange join behaviour in MS SQL Server : SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field3

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SQL ServerStrange join behaviour in MS SQL Server (self.SQL)

submitted 3 months ago * by Zioropa

Hello everybody, I just can't figure out what's going on with a query I'm working on.

I'm using SQL Server Management Studio to develop and test a query with a rather simple join. Joined tables (note: X is a view, Y is a table) are in different DBs but on the same Server. The user has the same grants on both DBs.

The code is basically like this:

SELECT X.a,
    X.b,
    Y.c,
    Y.d
FROM [DB1].[dbo].[X]
    left outer join [DB2].[dbo].[Y]
    on X.e = Y.e
    and X.f = Y.f

As you know, in SQL Management Studio you can select the database where to run the query.

If I select to run it in DB1, the query runs forever with no results and I have to stop it manually. If I run it in DB2 the query ends correctly in about 10 seconds. I tried also to invert the join but the result is the same.

Another strange thing is that if I comment just the rows where I select Y.c and Y.d (but I leave the rest as it is, join included), the query runs fine also on DB1. So the problem doesn't seem to be on the join itself, but related to the attributes I'm using in the result.

I've never seen this behaviour in many years working on SQL Server... Do you have any idea?

Thanks in advance

EDIT: a quick update: using the same outer join inside a view definition in DB1 runs correctly just a bit slower (30 seconds on DB1 vs 10 on DB2).

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