How to get substring in SQLsever by finding nth occurance of character - sql-server

Question

I have a varchar field in SQL Server 2008 like
colName_vch = 'field1;field2;field3;field4;field5;field6;field7'
I want the value of field4.
Now one long way is to do use RIGHT,CHARINDEX for ; and SUBSTRING in recursion, but that becomes very complex and increases query time.
Is there any other quick/less complex way for achieving this?
I know this is a bad DB design, but I am stuck with this for a while now.
Any help is appreciated!!

Answer 1

I'm not sure if i've really understood your question, but here is my guess:
You could write a custom Split function which splits by a delimiter(in this case ;). Then you can use ROW_NUMBER to get the desired part with a given index(4 here).
For example:
DECLARE #string VARCHAR(100);
SET #string='field1;field2;field3;field4;field5;field6;field7';
DECLARE #index INT;
SET #index = 4;
WITH cte
AS (SELECT item,
rn=Row_number()
OVER(
ORDER BY item)
FROM dbo.Split(#string, ';'))
SELECT TOP 1 item
FROM cte
WHERE rn = #index
Here a DEMO on sql-fiddle.
This is my split-function:
CREATE FUNCTION [dbo].[Split]
(
#ItemList NVARCHAR(MAX),
#delimiter CHAR(1)
)
RETURNS #IDTable TABLE (Item VARCHAR(50))
AS
BEGIN
DECLARE #tempItemList NVARCHAR(MAX)
SET #tempItemList = #ItemList
DECLARE #i INT
DECLARE #Item NVARCHAR(4000)
SET #tempItemList = REPLACE (#tempItemList, ' ', '')
SET #i = CHARINDEX(#delimiter, #tempItemList)
WHILE (LEN(#tempItemList) > 0)
BEGIN
IF #i = 0
SET #Item = #tempItemList
ELSE
SET #Item = LEFT(#tempItemList, #i - 1)
INSERT INTO #IDTable(Item) VALUES(#Item)
IF #i = 0
SET #tempItemList = ''
ELSE
SET #tempItemList = RIGHT(#tempItemList, LEN(#tempItemList) - #i)
SET #i = CHARINDEX(#delimiter, #tempItemList)
END
RETURN
END

Answer 2

CREATE FUNCTION dbo.SplitStrings
(
#List NVARCHAR(MAX),
#Delimiter NVARCHAR(255)
)
RETURNS #t TABLE([Index] INT IDENTITY(1,1), Item NVARCHAR(255))
AS
BEGIN
INSERT #t(Item) SELECT SUBSTRING(#List, Number,
CHARINDEX(#Delimiter, #List + #Delimiter, Number) - Number)
FROM (SELECT ROW_NUMBER() OVER (ORDER BY [object_id])
FROM sys.all_objects) AS n(Number)
WHERE Number <= CONVERT(INT, LEN(#List))
AND SUBSTRING(#Delimiter + #List, Number, 1) = #Delimiter
ORDER BY Number OPTION (MAXDOP 1);
RETURN;
END
GO
DECLARE #x TABLE(i INT, string NVARCHAR(4000));
INSERT #x SELECT 1, N'field1;field2;field3;field4;field5;'
UNION ALL SELECT 2, N'x;y;6;r;3;2;w;'
UNION ALL SELECT 3, N'ttt;444;rrr;333;111;444;777;888;';
SELECT x.i, s1.Item
FROM #x AS x
CROSS APPLY dbo.SplitStrings(x.string, ';') AS s1
WHERE s1.[Index] = 4;