Delete duplicate rows from the table using row_number()

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Delete duplicate rows from the table using row_number()

rajesh_friends2005

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September 6, 2010 at 10:56 pm

#237959

Comments posted to this topic are about the item Delete duplicate rows from the table using row_number()

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crackbridge SSC Enthusiast Points: 185 More actions · Answer 1

It's actually cool. Thanks a lot. Have you test it for large tables, with joins?

I have recently checked it uses to be faster sometimes to create the temporal table (t) instead of using that feature you have used, specially when further joins are going to be declared linking the "temporal" table created on the fly in this case inside parenthesis ()t.

Have a good day!

mtillman-921105 SSCertifiable Points: 7156 More actions · Answer 2

Very good! Thank you.

It surprises me that the DELETE statement works because I would have thought that the table would have to be explicitly named, but it works nevertheless.

The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge. - Stephen Hawking

SanDroid SSChampion Points: 10068 More actions · Answer 3

This was done in a single script, but not a single query.

The insert into the #temp table is executed as a seperate query.

You would need to start with the use of a WITH table statement, or a derived table to get this done to a single query.

Interesting way to resolve a bad table design issue without correcting the bad table design.

mtillman-921105 SSCertifiable Points: 7156 More actions · Answer 4

SanDroid (7/5/2011)
This was done in a single script, but not a single query.
The insert into the #temp table is executed as a sperate query.
You would need to start with the use of a WITH table statement, or a derived table to get this done to a single query.
Interesting way to resolve a bad table design issue without correcting the bad table design.

At times you have to work with less than perfect data even if it's no fault of your own.

Also, in my estimation, the "single query" push is a little overrated. What's the advantage of a single query? Performance can be enhanced in some cases with more than one query. So performance itself can't always be the answer.

The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge. - Stephen Hawking

SanDroid SSChampion Points: 10068 More actions · Answer 5

mtillman-921105 (7/5/2011)
SanDroid (7/5/2011)
This was done in a single script, but not a single query.
The insert into the #temp table is executed as a sperate query.
You would need to start with the use of a WITH table statement, or a derived table to get this done to a single query.
Interesting way to resolve a bad table design issue without correcting the bad table design.
At times you have to work with less than perfect data even if it's no fault of your own.
Also, in my estimation, the "single query" push is a little overrated. What's the advantage of a single query? Performance can be enhanced in some cases with more than one query. So performance itself can't always be the answer.

The name of the article compared to it's syntax and content inspired the entire post.

Please do not confuse my comments on the authors odd word choice in this article as a personal opinion on some subject that was not mentioned.

don 24688 SSC Rookie Points: 46 More actions · Answer 6

SanDroid (7/5/2011)
This was done in a single script, but not a single query.
The insert into the #temp table is executed as a seperate query.
You would need to start with the use of a WITH table statement, or a derived table to get this done to a single query.
Interesting way to resolve a bad table design issue without correcting the bad table design.

Maybe I'm wrong, but I think all of the #temp table stuff was just to have sample data to show how the technique works. He could have just written something like:

Delete T From

(Select Row_Number() Over(Partition By [fld1],[fld2],[fld3],[fld4] order By [fld1]) As RowNumber,* From [tablename])T

Where T.RowNumber > 1

and then explained that the partition clause needs to include all of the fields. Instead, he included a concrete example.

ken.trock SSCertifiable Points: 5147 More actions · Answer 7

Yeah, it's cool; I didn't know you could do this. I was getting this type of thing done by, and I'll use the C word, a cursor. 😀

Ken

umairjavedsheikh Grasshopper Points: 14 More actions · Answer 8

Thanks a lot for the script a rather easy and better way to do the job. 🙂

akljfhnlaflkj SSC Guru Points: 76202 More actions · Answer 9

akljfhnlaflkj

SSC Guru

Points: 76202

May 12, 2016 at 7:26 am

#1878603

Thanks for the script.

akljfhnlaflkj SSC Guru Points: 76202 More actions · Answer 10

umairjavedsheikh (4/18/2012)
Thanks a lot for the script a rather easy and better way to do the job. 🙂

Totally agree.