Efficient way to string split using CTE - sql

Question

I have a table that looks like
ID Layout
1 hello,world,welcome,to,tsql
2 welcome,to,stackoverflow
The desired output should be
Id Splitdata
1 hello
1 world
1 welcome
1 to
1 tsql
2 welcome
2 to
2 stackoverflow
I have done this by the below query
Declare #t TABLE(
ID INT IDENTITY PRIMARY KEY,
Layout VARCHAR(MAX)
)
INSERT INTO #t(Layout)
SELECT 'hello,world,welcome,to,tsql' union all
SELECT 'welcome,to,stackoverflow'
--SELECT * FROM #t
;With cte AS(
select F1.id
,O.splitdata
from
(
select *,
cast('<X>'+replace(F.Layout,',','</X><X>')+'</X>' as XML) as xmlfilter
from #t F
)F1
cross apply
(
select fdata.D.value('.','varchar(MAX)') as splitdata
from f1.xmlfilter.nodes('X') as fdata(D)) O
)
select * from cte
But performance wise it is very bad. I am looking for a more efficient query but using CTE only.

Answer 1

You seem dead set on using a CTE, so try this:
DECLARE #YourTable table (RowID int, Layout varchar(200))
INSERT #YourTable VALUES (1,'hello,world,welcome,to,tsql')
INSERT #YourTable VALUES (2,'welcome,to,stackoverflow')
;WITH SplitSting AS
(
SELECT
RowID,LEFT(Layout,CHARINDEX(',',Layout)-1) AS Part
,RIGHT(Layout,LEN(Layout)-CHARINDEX(',',Layout)) AS Remainder
FROM #YourTable
WHERE Layout IS NOT NULL AND CHARINDEX(',',Layout)>0
UNION ALL
SELECT
RowID,LEFT(Remainder,CHARINDEX(',',Remainder)-1)
,RIGHT(Remainder,LEN(Remainder)-CHARINDEX(',',Remainder))
FROM SplitSting
WHERE Remainder IS NOT NULL AND CHARINDEX(',',Remainder)>0
UNION ALL
SELECT
RowID,Remainder,null
FROM SplitSting
WHERE Remainder IS NOT NULL AND CHARINDEX(',',Remainder)=0
)
SELECT * FROM SplitSting ORDER BY RowID
OUTPUT:
RowID Part
----------- -----------------------
1 hello
1 world
1 welcome
1 to
1 tsql
2 welcome
2 to
2 stackoverflow
(8 row(s) affected)
here is an excellent article on splitting strings in SQL Server: "Arrays and Lists in SQL Server 2005 and Beyond, When Table Value Parameters Do Not Cut it" by Erland Sommarskog
EDIT here's another version (but you need a numbers table) returns same results as above:
;WITH SplitValues AS
(
SELECT
RowID,ListValue
FROM (SELECT
RowID, LTRIM(RTRIM(SUBSTRING(List2, number+1, CHARINDEX(',', List2, number+1)-number - 1))) AS ListValue
FROM (
SELECT RowID, ',' + Layout + ',' AS List2
FROM #YourTable
) AS dt
INNER JOIN Numbers n ON n.Number < LEN(dt.List2)
WHERE SUBSTRING(List2, number, 1) = ','
) dt2
WHERE ListValue IS NOT NULL AND ListValue!=''
)
SELECT * FROM SplitValues
see here for a numbers table: What is the best way to create and populate a numbers table?

Answer 2

From NullRef's Answer
Function without set operation will be faster according to my understanding of sql server
so this will be more efficient
CREATE FUNCTION fnSplitString(#str nvarchar(max),#sep nvarchar(max))
RETURNS TABLE
AS
RETURN
WITH a AS(
SELECT CAST(0 AS BIGINT) as idx1,CHARINDEX(#sep,#str) idx2
UNION ALL
SELECT idx2+1,CHARINDEX(#sep,#str,idx2+1)
FROM a
WHERE idx2>0
)
SELECT SUBSTRING(#str,idx1,COALESCE(NULLIF(idx2,0),LEN(#str)+1)-idx1) as value
FROM a

Answer 3

it's my best solution using CTE:
DECLARE #Char VARCHAR(MAX) = '10||3112||||aaaa||'
DECLARE #Separador CHAR(2) = '||'
;WITH Entrada AS(
SELECT
CAST(1 AS Int) As Inicio,
CHARINDEX(#Separador, #Char) As Fim
UNION ALL
SELECT
CAST(Fim + LEN(#Separador) AS Int) As Inicio,
CHARINDEX(#Separador, #Char, Fim + 1) As Fim
FROM Entrada
WHERE CHARINDEX(#Separador, #Char, Fim + 1) > 0
)
SELECT
SUBSTRING(#Char, Inicio, Fim - Inicio)
FROM Entrada
WHERE (Fim - Inicio) > 0