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SQL MAX  Help

Posted on 2014-09-03
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Last Modified: 2014-09-03
Hi,
I have a very simple select statement that returns this dataset

SELECT parent_id, component_id, control_id FROM item where parent_id = '14923'

parent_id      component_id      control_id
14923      12054      53715
14923      12054      53721
14923      12054      53715
14923      12054      53721
14923      12423      53715
14923      12423      53721
14923      14176      53715
14923      14176      53721
14923      14783      53715
14923      14783      53721
14923      14795      53715
14923      14795      53721
14923      14840      53715
14923      14840      53721
14923      14880      53715
14923      14880      53721
14923      14924      53715
14923      14924      53721
14923      14926      53715
14923      14926      53721


I need to add an additional where clause that only returns the highest control values, so in this case the returned dataset would look like this:

parent_id      component_id      control_id
14923      12054      53721
14923      12054      53721
14923      12423      53721
14923      14176      53721
14923      14783      53721
14923      14795      53721
14923      14840      53721
14923      14880      53721
14923      14924      53721
14923      14926      53721

Any suggestions as to how I can accomplish this please
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Question by:andyw27
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11 Comments
 
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Accepted Solution

by:
Dan Craciun earned 500 total points
ID: 40300878
Maybe something like this (untested):
SELECT parent_id, component_id, control_id 
FROM item 
WHERE parent_id = '14923' AND control_id = (SELECT MAX(control_id) FROM item WHERE parent_id = '14923')

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HTH,
Dan
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Expert Comment

by:Vikas Garg
ID: 40300879
HI,

Select Parent_id, Component_id, (select max(control_id) from table) ControlID from Table

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Expert Comment

by:Vitor Montalvão
ID: 40300884
Use the MAX() function:
SELECT parent_id, component_id, MAX(control_id)
FROM item 
WHERE parent_id = '14923'
GROUP BY parent_id, component_id

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LVL 65

Expert Comment

by:Jim Horn
ID: 40300894
The above answer is correct.

If you want to eliminate duplicates, use DISTINCT.
SELECT DISTINCT parent_id, component_id, MAX(control_id)
FROM item 
WHERE parent_id = '14923'
GROUP BY parent_id, component_id

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Also, if you'd like further reading on aggregates such as MAX then I have an article out there called SQL Server GROUP BY Solutions that would be an excellent reading.
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LVL 49

Expert Comment

by:Vitor Montalvão
ID: 40300904
Jim, you won't need the DISTINCT since it's already aggregate by parent_id and component_id so duplicates will be automatically dropped.
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Author Closing Comment

by:andyw27
ID: 40300907
Thanks, worked like a charm.
0
 
LVL 49

Expert Comment

by:Vitor Montalvão
ID: 40300916
Andy, any of these solutions works (Vikas forgot the WHERE clause) but there's no need to use subselects.
You can do it in a more direct and efficient way.

Cheers
0
 
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Expert Comment

by:Dan Craciun
ID: 40300922
Glad I could help!

@Vitor and Jim: on your queries, if a component_id does not have a row where control_id is 53721, it will be listed with the highest control_id value if finds. The OP wanted only rows where control_id is 53721. At least that's the way I understood the question.
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Expert Comment

by:Vitor Montalvão
ID: 40300931
Dan, I didn't understand the question like that:
where clause that only returns the highest control values
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LVL 15

Expert Comment

by:Vikas Garg
ID: 40300969
Hello,

SELECT parent_id, component_id, control_id FROM item a
INNER JOIN
(Select Parent_id, Component_id, (select max(control_id) from item) ControlID from item) B
ON A.parent_id = B.Parent_id AND A.component_id = B.component_id AND A.control_id = B.control_id
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Expert Comment

by:Jim Horn
ID: 40302021
Vitor - You are correct.  What was I thinking...
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