How to remove duplicates from a string in SQL
11,250
Option 1 with a Parse Function
Declare @YourTable table (ID int,YourCol varchar(50))
Insert Into @YourTable values
(1,'qw"qw"er"er'),
(2,'q"w"w"q'),
(3,'f"k"s"g')
Select A.ID
,A.YourCol
,DeDuped = Stuff((Select '"' + RetVal
From (Select RetSeq=Min(RetSeq),RetVal
From [dbo].[udf-Str-Parse](A.YourCol,'"')
Group By RetVal) P
Order by 1 For XML Path('')),1,1,'')
From @YourTable A
Returns
ID YourCol DeDuped
1 qw"qw"er"er qw"er
2 q"w"w"q q"w
3 f"k"s"g f"k"s"g
Option 2: Without a Parse Function
Declare @YourTable table (ID int,YourCol varchar(50))
Insert Into @YourTable values
(1,'qw"qw"er"er'),
(2,'q"w"w"q'),
(3,'f"k"s"g')
Select A.ID
,A.YourCol
,DeDuped = Stuff((Select '"' + RetVal
From (Select RetSeq=Min(RetSeq),RetVal
From (
Select RetSeq = Row_Number() over (Order By (Select null))
,RetVal = LTrim(RTrim(B.i.value('(./text())[1]', 'varchar(max)')))
From (Select x = Cast('<x>' + replace((Select replace(A.YourCol,'"','§§Split§§') as [*] For XML Path('')),'§§Split§§','</x><x>')+'</x>' as xml).query('.')) as A
Cross Apply x.nodes('x') AS B(i)
) P1
Group By RetVal) P
Order by RetSeq
For XML Path('')),1,1,'')
From @YourTable A
Returns
ID YourCol DeDuped
1 qw"qw"er"er qw"er
2 q"w"w"q q"w
3 f"k"s"g f"k"s"g
The UDF if Interested
CREATE FUNCTION [dbo].[udf-Str-Parse] (@String varchar(max),@Delimiter varchar(10))
Returns Table
As
Return (
Select RetSeq = Row_Number() over (Order By (Select null))
,RetVal = LTrim(RTrim(B.i.value('(./text())[1]', 'varchar(max)')))
From (Select x = Cast('<x>' + replace((Select replace(@String,@Delimiter,'§§Split§§') as [*] For XML Path('')),'§§Split§§','</x><x>')+'</x>' as xml).query('.')) as A
Cross Apply x.nodes('x') AS B(i)
);
--Thanks Shnugo for making this XML safe
--Select * from [dbo].[udf-Str-Parse]('Dog,Cat,House,Car',',')
--Select * from [dbo].[udf-Str-Parse]('John Cappelletti was here',' ')
--Select * from [dbo].[udf-Str-Parse]('this,is,<test>,for,< & >',',')
--Performance On a 5,000 random sample -8K 77.8ms, -1M 79ms (+1.16), -- 91.66ms (+13.8)
Author by
wouter de jong
Updated on June 04, 2022Comments
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wouter de jong almost 2 years
I got a column in my SQL table where some values are seperated bij
"
. Some values in this string are duplicated which I want to remove. Here is an example of my data:--------------- | qw"qw"er"er | --------------- | q"w"w"q | --------------- | f"k"s"g | ---------------
Now The result should replace any duplicates:
--------------- | qw"er | --------------- | q"w" | --------------- | f"k"s"g | ---------------
So first I want to split the string and then remove duplicates. Could anyone help me with this issue?
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Hassan Voyeau over 5 yearsCan this answer be updated with a shorter/easier answer? Or is it still this involved?
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John Cappelletti over 5 years@HassanVoyeau If you are on 2016+ you can use string_split() Take a peek at dbfiddle.uk/…
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John Cappelletti over 5 years@HassanVoyeau The Parse UDF is perhaps the most concise version avail prior to 2016
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John Cappelletti over 5 years@HassanVoyeau If 2017+ you could replace the XML STUFF portion with STRING_AGG()
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John Cappelletti over 5 years@HassanVoyeau One last point. The XML Parse function is VERY performant. On a sample size of 15,000 records it was 13ms slower than the tally approach, and it is not limited to 10K bytes