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Asked: 2026-05-16T07:35:33+00:00

HI all, I’m having some difficulty understanding the rationale behind group by aggregation in

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HI all,
I’m having some difficulty understanding the rationale behind group by aggregation in sql server 2005.

I have the following query which works fine and returns one row for each contact.id and the 1st occurence of event

SELECT
contact.id
,MIN(eve.date_created)
FROM _contact contact WITH(nolock)
INNER JOIN table2 tb2 WITH (nolock) ON contact.id = tb2.id1
INNER JOIN _event eve WITH (nolock) ON tb2.id2 = eve.id
INNER JOIN _cashtable cash WITH (nolock) ON cash.contact_id = contact.id
GROUP BY contact.id

However what I’m looking for is to have the following query and still only pull out one row per contact.id

SELECT
contact.id
,MIN(eve.date_created)
,cash.id2    -- the cash linked to the first event
,eve.id      -- the first event linked to the contact    
FROM _contact contact with (nolock)
INNER JOIN _table2 tb2 WITH (nolock) ON contact.id = tb2.id1
INNER JOIN _event eve WITH (nolock) ON tb2.id2 = eve.id
INNER JOIN _cashtable cash WITH (nolock) ON cash.contact_id = contact.id
GROUP BY contact.id

I get the standard error message saying that I need to add in cash.id2 and eve.id into the group by clause, which returns results I don’t want.

I know that there are the potential options of using rank() / partitioning
or even including the 

select(MIN(eve.date_created)

in the FROM clause, but I am not sure which would be best to put this and am still quite confused as to why SQL requires everything to be included in the group by statement and so any advice would be great 🙂

Thanks in advance!

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1 Answer

  1. Editorial Team

    I think you need a subquery joining the event table with an aggregation of itself returning only the min(event dates)

    SELECT
contact.id,min_created,cash.id2    -- the cash linked to the first event
,eve.id      -- the first event linked to the contact    
FROM _contact contact 
INNER JOIN _table2 tb2  ON contact.id = tb2.id1
INNER JOIN _event eve  ON tb2.id2 = eve.id
inner join (select id, date_created as min_created from _event group by id) eve_min
on eve_min.id = eve.id and eve_min.min_created = eve.date_created 
INNER JOIN _cashtable cash  ON cash.contact_id = contact.id
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