Get the last three values with in a delimited string using SQL Server - sql

Question

I would like to extract only the last three values from a delimited string and generate a delimited substring with those three values. Could anyone suggest what is the best way to do this. I tried using STRING_SPLIT and was able to successfully split the string into multiple values but I am not sure how to proceed further. Any thoughts would be appreciated.
SELECT value FROM STRING_SPLIT('CatalogTypeCode VARCHAR(10) NOT NULL
,EventID INT NOT NULL
,ModelCode TINYINT NOT NULL
,YearID INT NOT NULL
,PerilSetCode INT NOT NULL
,GrossLoss FLOAT NULL
,GrossSD FLOAT NULL
,GrossMaxLoss FLOAT NULL',',')
Output:
CatalogTypeCode VARCHAR(10) NOT NULL
EventID INT NOT NULL
ModelCode TINYINT NOT NULL
YearID INT NOT NULL
PerilSetCode INT NOT NULL
GrossLoss FLOAT NULL
GrossSD FLOAT NULL
GrossMaxLoss FLOAT NULL
Expected Output :
'GrossLoss FLOAT NULL,GrossSD FLOAT NULL,GrossMaxLoss FLOAT NULL'

Answer 1

Perhaps another option using a little XML in concert with reverse() ... twice
Example
Declare #YourTable table (ID int,SomeCol varchar(150))
Insert Into #YourTable values
(1,'Val1,Val2,Val3,Val4')
,(2,'Val1,Val2,Val3,Val4,Val5,Val6')
,(3,'Val1,Val2')
,(4,'Val1')
,(5,null)
Select A.ID
,LastThree = reverse(concat(Pos1,','+Pos2,','+Pos3))
From #YourTable A
Cross Apply (
Select Pos1 = n.value('/x[1]','varchar(max)')
,Pos2 = n.value('/x[2]','varchar(max)')
,Pos3 = n.value('/x[3]','varchar(max)')
From (Select cast('<x>' + replace(reverse(SomeCol),',','</x><x>')+'</x>' as xml) as n) X
) B
Returns
ID LastThree
1 Val2,Val3,Val4
2 Val4,Val5,Val6
3 Val1,Val2 -- Notice only 2 values
4 Val1 -- Notice only 1 value
5 -- Notice value was null

Answer 2

Unfortunately, split_string() doesn't return the position of the values within the string.
This will work, assuming there are no duplicates among the lines:
SELECT string_agg(line, ',') within group (order by pos) as lines_3
FROM (SELECT TOP (3) s.line, CHARINDEX(line, lines) as pos
FROM (VALUES ('CatalogTypeCode VARCHAR(10) NOT NULL
,EventID INT NOT NULL
,ModelCode TINYINT NOT NULL
,YearID INT NOT NULL
,PerilSetCode INT NOT NULL
,GrossLoss FLOAT NULL
,GrossSD FLOAT NULL
,GrossMaxLoss FLOAT NULL')
) v(lines) OUTER APPLY
STRING_SPLIT(v.lines, ',') s(line)
ORDER BY pos
) s
EDIT:
Oops, the above works on SQL Server 2017, but not 2016. You can use conditional aggregation:
SELECT (MAX(CASE WHEN seqnum = 1 THEN line END) + ','
MAX(CASE WHEN seqnum = 2 THEN line END) + ','
MAX(CASE WHEN seqnum = 3 THEN line END)
) as lines_3
FROM (SELECT TOP (3) s.line,
ROW_NUMBER() OVER (ORDER BY CHARINDEX(line, lines)) as seqnum
FROM (VALUES ('CatalogTypeCode VARCHAR(10) NOT NULL
,EventID INT NOT NULL
,ModelCode TINYINT NOT NULL
,YearID INT NOT NULL
,PerilSetCode INT NOT NULL
,GrossLoss FLOAT NULL
,GrossSD FLOAT NULL
,GrossMaxLoss FLOAT NULL')
) v(lines) OUTER APPLY
STRING_SPLIT(v.lines, ',') s(line)
ORDER BY pos
) s;

Answer 3

I am using this table-valued function for years now. Works fine. After creating function call select top 3 * from lma.dbo.split_test('a,b,c,d,e',',') order by id desc
CREATE FUNCTION [dbo].[Split]
(
#String VARCHAR(MAX),
#Delimiter VARCHAR(10)
)
RETURNS #Temptable TABLE (id int identity, items varchar(MAX))
AS
BEGIN
DECLARE #Idx INT
DECLARE #Slice VARCHAR(MAX)
DECLARE #Delimiterlen INT=LEN(#Delimiter)
--,#String VARCHAR(MAX)='N'
--,#Delimiter VARCHAR(10)=';;'
IF (#String like '%' + #Delimiter + '%')
BEGIN
SELECT #Idx = 1
IF LEN(#String)<#Delimiterlen or #String is null RETURN
WHILE #Idx!= 0
BEGIN
SET #Idx = CHARINDEX(#Delimiter,#String)
IF #Idx!=0
SET #Slice = left(#String,#idx-1)
ELSE
SET #Slice = #String
IF(LEN(#Slice)>0)
INSERT INTO #Temptable(Items) values(#Slice)
--290913 : IF WE WANT TO USE DELIMETER LENGTH GREATER THAN 2
IF LEN(#String) >= (#Idx -1 + #Delimiterlen)
SET #String = RIGHT(#String,LEN(#String) - (#Idx-1+#Delimiterlen))
IF LEN(#String) = 0 BREAK
END
END
ELSE
BEGIN
INSERT INTO #Temptable(Items) values(#String)
END
DELETE #Temptable WHERE items =''
RETURN
END