MS SQL order by with "over" statement and row_number()

I have a query I use frequently that someone helped me write several years ago, which I often create variations on. I thought I understood exactly what it does, but I am finding a discrepancy with the "order by" that I don't understand.

This query does what I want, which is simply an alphabetical sort on the "description" column:

select distinct
	description
from
	(select row_number() over (order by description) as rownum, description
		from tbl_product
		where (itemid='LUGS & H-TAPS : YAV2CLTC10FX' or itemid='LUGS & H-TAPS : YAV2CL2TC14E2FX')) as qryresults

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RESULT:

description
"LUG COMPRESSION # 2 AWG FLEX 1 HOLE #10 STUD STANDARD BARREL 0.68"" TONGUE WIDTH BROWN W/ INSP WNDW BURNDY"
"LUG COMPRESSION # 2 AWG FLEX 2 HOLE 1/4"" STUD 3/4"" CENTER STANDARD BARREL 0.68"" TONGUE WIDTH BROWN W/ INSP WNDW BURNDY"

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This query returns the same two results, but the "order by" is backwards:

select distinct
	itemid, description
from
	(select row_number() over (order by description) as rownum, itemid, description
		from tbl_product
		where (itemid='LUGS & H-TAPS : YAV2CLTC10FX' or itemid='LUGS & H-TAPS : YAV2CL2TC14E2FX')) as qryresults

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RESULT:

itemid 	description
LUGS & H-TAPS : YAV2CL2TC14E2FX	"LUG COMPRESSION # 2 AWG FLEX 2 HOLE 1/4"" STUD 3/4"" CENTER STANDARD BARREL 0.68"" TONGUE WIDTH BROWN W/ INSP WNDW BURNDY"
LUGS & H-TAPS : YAV2CLTC10FX	"LUG COMPRESSION # 2 AWG FLEX 1 HOLE #10 STUD STANDARD BARREL 0.68"" TONGUE WIDTH BROWN W/ INSP WNDW BURNDY"

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The only difference between the two is the "itemid" column present in the "select" clause (twice). I'm not understanding why selecting that column should cause the sorting to be backwards.

Thank you!
Brad BansnerWeb DeveloperAsked:
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Pawan KumarDatabase ExpertCommented:
In one query you are sorting on itemid, description and in another you are doing only on description.

Thats why.
, DISTINCT will give you distinct records, order will be decided on the columns selected.

Innner row_number() -- does not matter.
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Brad BansnerWeb DeveloperAuthor Commented:
I thought "order by description" would determine the order. I don't have "order by itemid,  description". How can I modify the second query so that it will return both itemid and description, but be sorted on description?
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Scott PletcherSenior DBACommented:
The ORDER BY in a ROW_NUMBER clause is used to assign values, it does not necessarily control the order in which rows are returned from the query.

An inner query order is never a guarantee of the order of rows for an outer query.

In short, if you want a specific order of rows returned by a query, you must ORDER BY in the outer query, such as:

select distinct
      itemid, description
from
      (select row_number() over (order by description) as rownum, itemid, description
            from tbl_product
            where (itemid='LUGS & H-TAPS : YAV2CLTC10FX' or itemid='LUGS & H-TAPS : YAV2CL2TC14E2FX')) as qryresults
order by description, itemid

Or even:

select distinct
      description
from
      (select row_number() over (order by description) as rownum, description
            from tbl_product
            where (itemid='LUGS & H-TAPS : YAV2CLTC10FX' or itemid='LUGS & H-TAPS : YAV2CL2TC14E2FX')) as qryresults
order by description

The distinct caused SQL to do a sort, which is why the rows were in order, but that was incidental/accidental, since an order by clause was not used.
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Pawan KumarDatabase ExpertCommented:
Here it is , You are not using row_num , why you have added it.

Sample example

select distinct
      itemid, description
from
      (select row_number() over (order by description) as rownum, itemid, description
            from tbl_product
            where (itemid='LUGS & H-TAPS : YAV2CLTC10FX' or itemid='LUGS & H-TAPS : YAV2CL2TC14E2FX')) as qryresults
ORDER BY description

select distinct
      description
from
      (select row_number() over (order by description) as rownum, description
            from tbl_product
            where (itemid='LUGS & H-TAPS : YAV2CLTC10FX' or itemid='LUGS & H-TAPS : YAV2CL2TC14E2FX')) as qryresults
ORDER BY description
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Brad BansnerWeb DeveloperAuthor Commented:
I guess I didn't understand that before. It always seemed to work in the past, maybe I just got lucky. Anyway, thanks for your help!
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Brad BansnerWeb DeveloperAuthor Commented:
I am using row_num in my final query, I was just trying to give you a stripped down version of my more complicated working query.
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Pawan KumarDatabase ExpertCommented:
Great that you got it !! Excellent.
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Brad BansnerWeb DeveloperAuthor Commented:
Sorry, I thought I had already assigned points.
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Scott PletcherSenior DBACommented:
Interesting points assignment.  Good luck with future qs.
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Brad BansnerWeb DeveloperAuthor Commented:
Oh geez, I apologize! I did not realize there was more than one respondent. Somehow missed that.
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Scott PletcherSenior DBACommented:
Oh, ok, that makes sense.  Now maybe it's just me, but I thought my comments were more useful and on point (of course, maybe that's just me favoring my own answer :-) ).

[To be clear, I am not suggesting he just copied my answer, as the times are extremely close, and cross-posting is unavoidable on a site like this.]
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