CWilson CWilson - 6 months ago 9
SQL Question

How can I perform aggregate function logic across multiple fields?

How can I get max() of three dimensions to come from the same record?

Description:
I have a large list of widgets, with multiple attributes, from multiple sources. Think manual data entry, where you have the same stuff being entered by different people, and then you need to consolidate differences. Though, instead of auditing each difference, I just want to perform some logic to choose a value over another under certain criteria.

An analogous example: if one source a says widget xyz weighs 3 pounds, and source b says it weighs 4 pounds, I am just blindly taking the 4, as it is greater, and say I need to be over cautious for packing/shipping purposes. That is easy, I choose MAX().

Now, I have a group of attributes that are in separate fields but related. Think dimensions of a box. There are width/length/height fields. If one source says the 'dimensions' are 2x3x4, and another says they are 3x3x4, I need to take the larger, for the same reason as above. Also sounds like MAX(), except...

My sources disagree on which is the width, height, or length. A 2x3x4 box could be entered 4x3x2, or 2x4x3, depending on how the source was looking at it. If I took the MAX of 3 such sources, I would end up with 4x4x4, even though all 3 sources measured it correctly. This is undesirable.

How do I take the greatest 'measurement' value, but make sure all three values comes from the same record?

If 'greatest' is impossible, we could settle for unique... except there is a fourth source, which has 0x0x0 for about 40% of the widgets. I can't leave a 0x0x0 if any of the other sources did in fact measure that widget.

some sample data

ID,widget_name,height,width,leng
(a1,widget3,2,3,4)
(b1,widget3,2,4,3)
(c1,widget3,4,3,2)
(d1,widget3,0,0,0)


output should be
(widget3,4,3,2)

Answer

you could use row_number instead of group by like

select * from 
(select data, ID,widget_name,height,width,leng, ROW_NUMBER() over ( partition by widget_name order by height + width + leng desc ) rowid
from yourTable
) as t
where rowid = 1