I am writing this query to display a bunch of Names from a table filled automatically from an outside source:
select MAX(UN_ID) as [ID] , MAX(UN_Name) from UnavailableNames group by (UN_Name)
I have a lot of name duplicates, so I used "Group by"
I want to delete all the duplicates right after I do this select query..
(Delete where the field UN_Name is available twice, leave it once)
Any way to do this?
Something likes this should work:
WITH CTE AS
(
SELECT rn = ROW_NUMBER()
OVER(
PARTITION BY UN_Name
ORDER BY UN_ID ASC), *
FROM dbo.UnavailableNames
)
DELETE FROM cte
WHERE rn > 1
You basically assign an increasing "row number" within each group that shares the same "un_name".
Then you just delete all rows which have a "row number" higher than 1 and keep all the ones that appeared first.
With CTE As
(
Select uid,ROW_NUMBER() OVER( PARTITION BY uname order by uid) as rownum
From yourTable
)
Delete
From yourTable
where uid in (select uid from CTE where rownum> 1 )
Related
As you can see below, I'm able to select all the row_numbers that are duplicates. I identified them using a window function ROW_NUMBER()
Although I want to delete them from the database.
How can I change my code to remove the duplicates identified, as I'm currently getting an error
WITH RowNumCTE AS (
SELECT *,
ROW_NUMBER() OVER (
PARTITION BY ParcelID,
PropertyAddress,
SalePrice,
SaleDate,
LegalReference
ORDER BY
UniqueID
) row_num
FROM housing_data
)
SELECT *
FROM RowNumCTE
WHERE row_num > 1
Duplicates are identified as having a row_number greater than 1.
Thanks
I found the solution. I used
DELETE FROM housing_data
WHERE ROWID NOT IN (
SELECT MIN(ROWID)
FROM housing_data
GROUP BY ParcelID, PropertyAddress, SalePrice, SaleDate, LegalReference
);
I have a table as shown in the image.In Number column, the values are appeared more than once (for example 63 appeared twice). I would like to keep only one value. Please see my code:
delete from t1 where
(SELECT *,row_number() OVER (
PARTITION BY
Number
ORDER BY
Date) as rn from t1 where rn > 1)
It shows error. Can anyone please assist.
enter image description here
The column created by row_number() was not accessed by your main query, in order to enable that, you can create a quick sub query and use the desired filter
SELECT *
FROM
(
SELECT *,
row_number() OVER (PARTITION BY Number ORDER BY Date) as rn
FROM t1 ) T
where rn = 1;
The partition by determines how row numbers repeat. The row numbers are assigned per group of partition by keys. So, you can get duplicates.
If you want a unique row number over all rows, just leave out the partition by:
select t1.*
from (select t1.*,
row_number() over (order by date) as rn
from t1
) t1
where rn > 1
if you want to keep only one value, rn = 1 instead of "> 1"
I have the following SQL select. How can I convert it to a delete statement so it keeps 1 of the rows but deletes the duplicate?
select s.ForsNr, t.*
from [testDeleteDublicates] s
join (
select ForsNr, period, count(*) as qty
from [testDeleteDublicates]
group by ForsNr, period
having count(*) > 1
) t on s.ForsNr = t.ForsNr and s.Period = t.Period
Try using following:
Method 1:
DELETE FROM Mytable WHERE RowID NOT IN (SELECT MIN(RowID) FROM Mytable GROUP BY Col1,Col2,Col3)
Method 2:
;WITH cte
AS (SELECT ROW_NUMBER() OVER (PARTITION BY ForsNr, period
ORDER BY ( SELECT 0)) RN
FROM testDeleteDublicates)
DELETE FROM cte
WHERE RN > 1
Hope this helps!
NOTE:
Please change the table & column names according to your need!
This is easy as long as you have a generated primary key column (which is a good idea). You can simply select the min(id) of each duplicate group and delete everything else - Note that I have removed the having clause so that the ids of non-duplicate rows are also excluded from the delete.
delete from [testDeleteDublicates]
where id not in (
select Min(Id) as Id
from [testDeleteDublicates]
group by ForsNr, period
)
If you don't have an artificial primary key you may have to achieve the same effect using row numbers, which will be a bit more fiddly as their implementation varies from vendor to vendor.
You can do with 2 option.
Add primary-key and delete accordingly
http://www.mssqltips.com/sqlservertip/1103/delete-duplicate-rows-with-no-primary-key-on-a-sql-server-table/
'2. Use row_number() with partition option, runtime add row to each row and then delete duplicate row.
Removing duplicates using partition by SQL Server
--give group by field in partition.
;with cte(
select ROW_NUMBER() over( order by ForsNr, period partition ForsNr, period) RowNo , * from [testDeleteDublicates]
group by ForsNr, period
having count(*) > 1
)
select RowNo from cte
group by ForsNr, period
Here are the columns in my table:
Id
EmployeeId
IncidentRecordedById
DateOfIncident
Comments
TypeId
Description
IsAttenIncident
I would like to delete duplicate rows where EmployeeId, DateOfIncident, TypeId and Description are the same - just to clarify - I do want to keep one of them. I think I should be using the OVER clause with PARTITION, but I am not sure.
Thanks
If you want to keep one row of the duplicate-groups you can use ROW_NUMBER. In this example i keep the row with the lowest Id:
WITH CTE AS
(
SELECT rn = ROW_NUMBER()
OVER(
PARTITION BY employeeid, dateofincident, typeid, description
ORDER BY Id ASC), *
FROM dbo.TableName
)
DELETE FROM cte
WHERE rn > 1
use this query without using CTE....
delete a from
(select id,name,place, ROW_NUMBER() over (partition by id,name,place order by id) row_Count
from dup_table) a
where a.row_Count >1
You can use the following query. This has an assumption that you want to keep the latest row and delete the other duplicates.
DELETE [YourTable]
FROM [YourTable]
LEFT OUTER JOIN (
SELECT MAX(ID) as RowId
FROM [YourTable]
GROUP BY EmployeeId, DateOfIncident, TypeId, Description
) as KeepRows ON
[YourTable].ID = KeepRows.RowId
WHERE
KeepRows.RowId IS NULL
I have a table which stores data where accidentally data has been stored multiple times because of case sensivity for the username field on server side code. The username field should be regarded as case insensitive. The important columns and data for the table can be found below.
My requirements now is to delete all but the most recent saved data. I'm writing an sql script for this, and started out by identifying all rows that are duplicates. This selection returns a table like below.
For each row, the most recent save is LASTUPDATEDDATE if it exist, otherwise CREATEDDATE. For this example, the most recent save for 'username' would be row 3.
ID CREATEDDATE LASTUPDATEDDATE USERNAME
-- ----------- --------------- --------
1 11-NOV-11 USERNAME
2 01-NOV-11 02-NOV-11 username
3 8-JAN-12 USERname
My script (which selects all rows where a duplicated username appears) looks like:
SELECT
id, createddate, lastupdateddate, username
FROM
table
WHERE
LOWER(username)
IN
(
SELECT
LOWER(username)
FROM
table
GROUP BY
LOWER(username)
HAVING
COUNT(*) > 1
)
ORDER BY
LOWER(username)
My question now is: How do I select everything but row 3? I have searched Stack Overflow for a good match to this question, but found no match good enough. I know I probably have to make a join of some kind, but can't really get my head around it. Would be really thankful for a push in the right direction.
We are using SQL Server, probably a quite new version.
To delete duplicates, you can use:
with todelete as (
select t.*,
row_number() over (partition by lower(username) order by createddate desc) as seqnum
from table
)
delete from t
where seqnum > 1
This assigns a sequential number to each row, starting with 1 for the most recent. It then deletes all but the most recent.
For two dates, you can use:
with todelete as (
select t.*,
row_number() over (partition by lower(username) order by thedate desc) as seqnum
from (select t.*,
(case when createddate >= coalesdce(updateddate, createddate)
then createddate
else updateddate
end) as thedate
from table
) t
)
delete from t
where seqnum > 1
A couple of things to note -- there is no reason to use LOWER in your query. A = a in SQL Server.
Also, to get the correct date, you can use COALESCE to determine if LastUpdatedDate exists and if so, sort by it, else sort by CreatedDate.
Putting that together, this should work:
DELETE T
FROM YourTable T
JOIN (
SELECT *, ROW_NUMBER() OVER (PARTITION BY username
ORDER BY COALESCE(lastupdateddate, createddate) DESC) as RN
FROM YourTable
) T2 ON T.Id = T2.Id
WHERE T2.RN > 1
Here is a sample fiddle: http://www.sqlfiddle.com/#!3/51f7c/1
As #Gordon correctly suggests, you could also use a CTE depending on the version of SQL Server you use (2005+):
WITH CTE AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY username
ORDER BY COALESCE(lastupdateddate, createddate) DESC) as RN
FROM YourTable
)
DELETE FROM CTE WHERE RN > 1