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SPLIT Function


SPLIT Function

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Bhushan
Bhushan
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Comments posted to this topic are about the item SPLIT Function



RD Francis
RD Francis
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Umm, you might want to change your description. The COALESCE function built into SQL Server does not create a concatenated string out of a list of values. From BOL:

COALESCE
Returns the first nonnull expression among its arguments.

If you're referring to a COALESCE UDF, you might want to try to point the user to that function as well.

Just FYI - presumably, I'm the only one of the hundreds of people who read this who's anal-retentive enough to bring it up....


R David Francis
Jeff Moden
Jeff Moden
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Heh... my concern is that UDF's of this nature qualify as RBAR... you get to split exactly one row. That's fine for a single parameter passed in from a GUI, but if you want to split a whole column in a table, you can use a Tally table to do the whole table at once. For example...

--===== Create a test table and some CSV data
-- This is NOT part of the solution... just building test data here
CREATE TABLE #CsvTest (SomeID INT PRIMARY KEY, SomeCsv VARCHAR(200))
INSERT INTO #CsvTest
(SomeID,SomeCsv)
SELECT 1,'Part01,Part02,Part03,Part04,Part05,Part06,Part07,Part08,Part09,Part10' UNION ALL
SELECT 2,'Part01,,Part03,Part04,Part05,Part06,Part07,,Part09,Part10' UNION ALL
SELECT 3,'Part01,Part02,Part03,,Part05,Part06,Part07,Part08,Part09,Part10' UNION ALL
SELECT 4,'Part01,Part02,Part03,Part04,Part05,,Part07,Part08,Part09,Part10' UNION ALL
SELECT 5,'Part01' UNION ALL
SELECT 6,'Part01,Part02' UNION ALL
SELECT 7,',Part02,Part03,Part04,Part05,Part06,Part07,Part08,Part09,' UNION ALL
SELECT 8,NULL UNION ALL
SELECT 9,'' UNION ALL
SELECT 10,','

--===== Split the whole CSV column using a single select with a cross join to the Tally table.
SELECT SomeID,
ElementNum = t.N-LEN(REPLACE(LEFT(','+ct.SomeCsv+',',t.N), ',', '')),
Value = NULLIF(SUBSTRING(','+ct.SomeCsv+',',t.N+1,CHARINDEX(',',','+ct.SomeCsv+',',t.N+1)-t.N-1),' ')
FROM #CsvTest ct
CROSS JOIN dbo.Tally t
WHERE t.N < LEN(','+ct.SomeCsv+',')
AND SUBSTRING(','+ct.SomeCsv+',',N,1) = ','
ORDER BY SomeID,ElementNum

DROP TABLE #CsvTest



...and, just in case you don't know how to make the wonderful little helper table known as a Tally table (it's got LOTS of uses), here's how...
--===== Create and populate the Tally table on the fly
SELECT TOP 11000 --equates to more than 30 years of dates
IDENTITY(INT,1,1) AS N
INTO dbo.Tally
FROM Master.dbo.SysColumns sc1,
Master.dbo.SysColumns sc2

--===== Add a Primary Key to maximize performance
ALTER TABLE dbo.Tally
ADD CONSTRAINT PK_Tally_N
PRIMARY KEY CLUSTERED (N) WITH FILLFACTOR = 100

--===== Allow the general public to use it
GRANT SELECT ON dbo.Tally TO PUBLIC



Of course, we all know it's a mortal database sin to store delimited data in a column... right? Wink

--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.
Although they tell us that they want it real bad, our primary goal is to ensure that we dont actually give it to them that way.
Although change is inevitable, change for the better is not.
Just because you can do something in PowerShell, doesnt mean you should. Wink

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