Introduction to STRING_SPLIT function in SQL

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Introduction to STRING_SPLIT function in SQL

Archana

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Points: 332
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February 27, 2020 at 12:00 am

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Comments posted to this topic are about the item Introduction to STRING_SPLIT function in SQL

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Japie Botma SSCrazy Points: 2990 More actions · Answer 1

This looks like an overkill to me. It is another help to people to understand STRING_SPLIT, but in your scenario I would use INSTR to get the positions of the dots and the LEFT and SUBSTRING concatenated to return the result. Or am I missing something?

5ilverFox
Consulting DBA / Developer
South Africa

Robert-378556 SSCertifiable Points: 5917 More actions · Answer 2

The problem with this solution is that the UDF assumes the same order of rows as the substrings in the input string, while the documentation for string_split says the order is not guaranteed.

aklt SSC Veteran Points: 233 More actions · Answer 3

My own horrible solution (which i think is something along the lines of what Japie Botma had in mind)

SELECT * INTO #TempWork FROM (
SELECT 'RCX_M01_SMD 1.0.6'AS AppVersion UNION
SELECT 'RCX_D00_BackOffice 7.2.1.0'AS AppVersion UNION
SELECT 'RCX_I04_OLAP 2.0.0.0 [2.0.0.5]' AS AppVersion UNION
SELECT 'RCX_X02_MOB 10.6.2.3'AS AppVersion 
) temp
GO
with cte as 
(
SELECT *, CHARINDEX('.', AppVersion, CHARINDEX('.', AppVersion, CHARINDEX('.', AppVersion, 0) + 1) + 1) Pos FROM #TempWork
), cte2 as 
(
select *, case when Pos = 0 then Len(AppVersion) else Pos - 1 end Length from cte
) 
select *, SUBSTRING(AppVersion, 1, Length) from cte2
GO

Japie Botma SSCrazy Points: 2990 More actions · Answer 4

Not quite. Something much simpler:

My Test Code:

SELECT 'RCX_M01_SMD 1.0.6 ' AS AppVersion INTO #Temp

INSERT INTO #Temp SELECT 'RCX_D00_BackOffice 7.2.1.0'

INSERT INTO #Temp SELECT 'RCX_I04_OLAP 2.0.0.0 [2.0.0.5]'

INSERT INTO #Temp SELECT 'RCX_X02_MOB 10.6.2.3'

SELECT AppVersion, dbo.fncBudleVersion(AppVersion) AS BundleVersion

FROM #Temp

DROP TABLE #Temp

My Function :

CREATE FUNCTION dbo.fncBudleVersion

(

@AppVersion VARCHAR(MAX)

)

RETURNS VARCHAR(MAX)

AS

BEGIN

DECLARE @Pos INT

SET @Pos = CHARINDEX('.', @AppVersion, 1)

SET @Pos = CHARINDEX('.', @AppVersion, @Pos + 1)

IF @Pos = 0 SET @Pos = LEN(@AppVersion) + 1

RETURN SUBSTRING(@AppVersion, 1, @Pos - 1)

END

5ilverFox
Consulting DBA / Developer
South Africa

Japie Botma SSCrazy Points: 2990 More actions · Answer 5

The same as yours, just with a function, because that was what he was using.

5ilverFox
Consulting DBA / Developer
South Africa

Xedni SSCertifiable Points: 6951 More actions · Answer 6

Robert-378556 wrote:

The problem with this solution is that the UDF assumes the same order of rows as the substrings in the input string, while the documentation for string_split says the order is not guaranteed.

I had the same thought. Imho the lack of straightforward ability to return the split values sorted makes the function useless in a great many scenarios. Shame...

Executive Junior Cowboy Developer, Esq.[/url]

Jeff Moden SSC Guru Points: 1004290 More actions · Answer 7

First of all, I appreciate it when anyone puts the time and effort into writing and publishing an article, so thank you very much for that. Keep writing.

As you've seen in the discussion above, so far, there are a couple of problems that people have cited and a couple they have not. I realize that some of these aren't even close to the primary thrust of your article but let's check out a couple of options...

Test Data

First, we need to duplicate the test data you posted for others to test with. I threw in a couple of wild geese just in case such things might occur.

--      DROP TABLE #TempWork
--===== Create the test table and populate it on-the-fly
 SELECT AppVersion
   INTO #TempWork 
   FROM (VALUES
         ('RCX_M01_SMD 1.0.6')
        ,('RCX_D00_BackOffice 7.2.1.0')
        ,('RCX_I04_OLAP 2.0.0.0 [2.0.0.5]')
        ,('RCX_X02_MOB 10.6.2.3')
        ,('RCX_J01_NoRbar 100.10') --Added the following rows just to be sure
        ,('RCX_J02_NoRbar 99')
        ,('RCX_J03_NoRbar')
        ) v (AppVersion)
;
GO

Should have been an "iSF"

In that latter category, you've built a Scalar UDF, which don't perform well for a lot of reasons we'll not cover in this post. What you should have done is to build it as an iSF (Inline Scalar Function) and, no... I'm not talking about 2019. In this case, an iSF is an iTVF (Inline Table Valued Function) that returns a scalar value. Please see the following article for more about this particular subject.

https://www.sqlservercentral.com/articles/how-to-make-scalar-udfs-run-faster-sql-spackle

Here's what the code for that rendition would look like along with an example call. Please DO observe the warning, which other people have also warned about. THIS CODE IS FOR DEMONSTRATION PURPOSES ONLY!!!

/***WARNING***WARNING***WARNING***WARNING***WARNING***WARNING***WARNING***
DO NOT USE THIS CODE IN PRODUCTION BECAUSE STRING_SPLIT IS NOT GUARANTEED
TO RETURN DATA ELEMENTS IN THE SAME ORDER AS THEY APPEAR IN THE STRING!!!
***WARNING***WARNING***WARNING***WARNING***WARNING***WARNING***WARNING***/
CREATE FUNCTION dbo.udf_GetBundleVersionUsingStringSplit_JBM01
        (
         @AppVersion VARCHAR(8000)
        )
RETURNS TABLE WITH SCHEMABINDING AS
 RETURN WITH
cte_StringSplit AS 
(--==== Split the string keep only the "first" 3 elements of the split
 SELECT TOP 3 
        StringSplitValue = split.[value]
   FROM STRING_SPLIT (@AppVersion,'.') split
)--==== Concatenate the pieces back together as a single string
 SELECT BundleVersion = STRING_AGG(StringSplitValue,'.')
   FROM cte_StringSplit
;
GO
--===== Demonstrate the usage of the function
 SELECT tw.AppVersion, ca.BundleVersion
   FROM #TempWork tw
  CROSS APPLY dbo.udf_GetBundleVersionUsingStringSplit_JBM01(tw.AppVersion) ca
;

Interesting Code

I liked the code that @ aklt posted. He used cCTEs (Cascading CTEs ) to DRY out the code. It, too, could be used in an iSF for reuse.

It IS a real shame...

It IS a real shame that Microsoft stuffed up what would have been a great splitter function by not including the ordinal position of the elements returned in the STRING_SPLIT function. If they did, the code would be super simple and you wouldn't even need to think about creating a function for the problem you've portrayed. I'm using the DelimitedSplit8K function to substitute as a better splitter that does return ordinal positions of the split out elements just to show what "could be". Notice the "sort" being done by the STRING_AGG()...

 SELECT  tw.AppVersion
        ,BundleVersion = STRING_AGG(split.Item,'.') WITHIN GROUP (ORDER BY split.ItemNumber ASC)
   FROM #TempWork tw
  CROSS APPLY dbo.DelimitedSplit8K(AppVersion,'.') split  --This takes the place of STRING_SPLIT()
  WHERE split.ItemNumber <=3
  GROUP BY tw.AppVersion
;

A recommendation

I recommend that you replace your current code with what @ aklt posted because it IS guaranteed to return everything in the correct order where yours is not. You can convert his code to an iSF for reasons of performance, as well.

Again, nice job on the article. Keep writing.

p.s.

You can get the DelimitedSplit8K function at the bottom of the following article in resources section. It works in all versions of SQL Server from 2005 and up.

https://www.sqlservercentral.com/articles/tally-oh-an-improved-sql-8k-%e2%80%9ccsv-splitter%e2%80%9d-function

If you have 2012 or up, a good friend of mine (Eirikur Eiriksson) made even that twice as fast by using LEAD, which first appeared in 2012. His rendition of the function is located in the first section of the following article...

https://www.sqlservercentral.com/articles/reaping-the-benefits-of-the-window-functions-in-t-sql-2

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Archana Old Hand Points: 332 More actions · Answer 8

Thank you, everyone, for your comments. I'm really inspired by all the discussions that are prevailing.

@jeff-moden, Thank you for the detailed explanation. It really helped me understand the gap.

Jeff Moden SSC Guru Points: 1004290 More actions · Answer 9

You're welcome and thank you for the feedback.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)