asked on
Problem deleting duplicates using a CTE when there are table joins
I've used CTEs to remove duplicates successfully before, but this time round I wanted to delete them from one table having joined to other tables and it comes back with the error:
View or function 'dupnotesCTE' is not updatable because the modification affects multiple base tables. See the attached code for my sql statement.
Not sure where I've gone wrong here...can someone help please?
View or function 'dupnotesCTE' is not updatable because the modification affects multiple base tables. See the attached code for my sql statement.
Not sure where I've gone wrong here...can someone help please?
;WITH dupnotesCTE([FileNo]
,[CommentDate]
,[CommentTime]
,[CommentUser]
,[Cat]
,[Pri]
,[Line]
,[Note], Ranking)
AS
(
SELECT p.[FileNo]
,p.[CommentDate]
,p.[CommentTime]
,p.[CommentUser]
,p.[Cat]
,p.[Pri]
,p.[Line]
,p.[Note]
,Ranking = row_number() OVER(PARTITION BY p.[FileNo]
,p.[CommentDate]
,p.[CommentTime]
,p.[CommentUser]
,p.[Cat]
,p.[Pri]
,p.[Line]
,p.[Note] ORDER BY p.[FileNo]
,p.[CommentDate]
,p.[CommentTime]
,p.[CommentUser]
,p.[Cat]
,p.[Pri]
,p.[Line]
,p.[Note])
FROM filenotes p
join detailtable d on ltrim(rtrim(p.FileNo)) = ltrim(rtrim(d.FileNo))
join country c on d.country_no = c.country_no
where c.continent in ('Asia','Europe')
)
delete from dupnotesCTE
where ranking > 1
Microsoft SQL Server 2005
Last Comment
Martin Griffiths
ASKER
This won't work though will it as, say you have a pair of duplicates A and B. You have A in dupnotesCTE with rank 1, and B in dupnotesCTE with rank 2. When you link from filenotes to dupnotes you'll have 4 records:
filenotes.A and dupnotes.A (rank 1)
filenotes.A and dupnotes.B (rank 2)
filenotes.B and dupnotes.A (rank 1)
filenotes.B and dupnotes.B (rank 2)
Your "where c.ranking > 1" will remove the 2nd and 4th combinations but you're left with two records i.e. combinations 1 and 3 above.
May be mistaken, but my query seems to reflect this.
filenotes.A and dupnotes.A (rank 1)
filenotes.A and dupnotes.B (rank 2)
filenotes.B and dupnotes.A (rank 1)
filenotes.B and dupnotes.B (rank 2)
Your "where c.ranking > 1" will remove the 2nd and 4th combinations but you're left with two records i.e. combinations 1 and 3 above.
May be mistaken, but my query seems to reflect this.
Does filenotes table have an identity column or primary key that you could use to join the cte?
ASKER
No it doesn't sorry.
So all of the columns with the duplicate FileNo are also duplicate?
ASKER
Yes, all the fields per fileno duplicate are identical i.e. a true duplicated record with the same data in each column:
[FileNo],[CommentDate],[Co
[FileNo],[CommentDate],[Co
Having an identity column would greatly simplify identifying the duplicates.
One possibility would be to copy the records over to a temp table with an identity column.
Remove the duplicates from the temp table.
Delete all the records from the user table that you originally copied to the temp table.
Insert the cleaned records back into filenotes table.
Here are some other alternatives:
"How to delete duplicate records or rows among identical rows in a table where no primary key exists"
http://www.kodyaz.com/articles/delete-duplicate-records-rows-in-a-table.aspx
One possibility would be to copy the records over to a temp table with an identity column.
Remove the duplicates from the temp table.
Delete all the records from the user table that you originally copied to the temp table.
Insert the cleaned records back into filenotes table.
Here are some other alternatives:
"How to delete duplicate records or rows among identical rows in a table where no primary key exists"
http://www.kodyaz.com/articles/delete-duplicate-records-rows-in-a-table.aspx
ASKER
I've added an identity column to the filenotes table now. How should it look now? Do I do something like at the bottom of your last link in method 3?
ASKER CERTIFIED SOLUTION
THIS SOLUTION ONLY AVAILABLE TO MEMBERS.
View this solution by signing up for a free trial.
Members can start a 7-Day free trial and enjoy unlimited access to the platform.
ASKER
That's worked a dream thanks Eric.
...
delete p
FROM filenotes p
JOIN dupnotesCTE c ON c.FileNo = p.fileNo --??
where c.ranking > 1