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Question about HAVING clause

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Question about HAVING clause MS SQL Development forum discussing administration, MS SQL queries, and other MS SQL-related topics. SQL Server is Microsoft's enterprise database engine.

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  #1  
Old August 4th, 2004, 05:38 AM
gobears03 gobears03 is offline
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Question about HAVING clause
Hello,

I'm working on this query that's supposed to give me a list of registered user's last_name, first_name, id and also the count on the number of visits during a time period:

Quote:
SELECT DISTINCT person.last_name AS l_name, person.first_name
AS f_name, person.id AS idnum, count (*) AS num_visits
FROM person, trail
WHERE person.last_name IS NOT NULL AND
person.id = trail.person_id AND
EXISTS
(select person.id, count (*) from person, trail group by
person.id HAVING count(*) >= 2 )
AND (trail.creation_date BETWEEN 'Jan 1 1997 00:00AM'
AND 'Jan 1 2000 11:59PM')
GROUP BY person.id, person.last_name, person.first_name
ORDER BY person.last_name, person.first_name ASC ;



However, if I change the count(*) >= 2 to be count(*) > 20 for example, it gives me the same rows as would >=2.

I would appreciate any insight. Thanks very much!
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  #2  
Old August 4th, 2004, 06:09 AM
pickledshark pickledshark is offline
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Quote:
AND EXISTS (select person.id, count (*) from person, trail group by
person.id HAVING count(*) >= 2 )


tie the two tables together in this subquery:

Quote:

AND EXISTS (select person.id, count (*) from person, trail
WHERE person.id = trail.person_id
group by person.id
HAVING count(*) >= 2 )
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  #3  
Old August 4th, 2004, 06:20 AM
gobears03 gobears03 is offline
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Quote:
Originally Posted by pickledshark
tie the two tables together in this subquery:


Hm.. after testing your proposed solution, it doesn't seem to change the results. ie. >=2 still gives results that have a frequency = 1....

But thanks a lot for your response, pickledshark
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  #4  
Old August 4th, 2004, 07:31 AM
pickledshark pickledshark is offline
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When you say frequency, is this a column? or is this the number of records in the table 'trail' for a given person?
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Old August 4th, 2004, 04:17 PM
gobears03 gobears03 is offline
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It is a column in the results table, coming from the count(*) query. But in other words, yes: the number of records in the table 'trail' for a given person record in the person table.
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