SQL Compare varchar variable with another varchar variable

Question

I have a Table name lines which has BillId (int) and LineReference (Varchar(100) as two columns. Each billid has LineReference value. However, value in the LineReference might n

Answer 1

--Create temp table and inserting data:
DECLARE @BillsRefs TABLE (
    BillId int, 
    LineReference nvarchar(100)
)

INSERT INTO @BillsRefs VALUES
(100,      '1,2,'),
(100,      '1,2,40,34'),
(100,      '1'),
(100,      '12')

--Declare variables
DECLARE @iCountRef varchar(100) = '1,2,3',
        @xml xml, @iXml xml

--Convert @iCountRef in XML
SELECT @iXml = CAST('' + REPLACE(@iCountRef,',','') + '' as xml)

--@iXml:
--1
--2
--3

--Convert table with data in XML
SELECT @xml = (
SELECT CAST('' + REPLACE(LineReference,',','') + '' as xml) 
FROM @BillsRefs
FOR XML PATH('')
)
--@xml:
--
--  1
--  2
--  
--
--
--  1
--  2
--  40
--  34
--
--
--  1
--
--
--  12
--

--Compare values from temp table to @iCountRef
--we convert string to xml - to convert them intoi tables
;WITH final AS (
SELECT DISTINCT
        t.v.value('../@id','nvarchar(100)') as LineReferenceOld, -- @id to take 'id="1,2,40,34"' from xml above
        CASE WHEN s.g.value('.','int') IS NULL THEN 1 ELSE s.g.value('.','int') END as LineReference 
        -- '.' is used to take value inside closed tags
FROM @xml.nodes('/s/a') as t(v) --we takes @xml (look above) and play with its nodes 's' (root for each @id) and `a`
LEFT JOIN @iXml.nodes('/b') as s(g) --we takes @iXml it has only 'b' tags
    ON t.v.value('.','int') = s.g.value('.','int') --here we JOIN both xml by `a` and `b`  tags
)

--In final table we get this:

--LineReferenceOld  LineReference
--1,2,              2
--12                    1
--1,2,40,34         1
--1,2,40,34         2
--1                 1
--1,2,              1

--Final SELECT
SELECT c.BillId,
        STUFF((SELECT DISTINCT  ','+CAST(f.LineReference as nvarchar(10))
        FROM final f
        WHERE c.LineReference = f.LineReferenceOld
        FOR XML PATH('')),1,1,'') as LineReference
FROM @BillsRefs c 

Output:

BillId  LineReference
100     1,2
100     1,2
100     1
100     1

If you need to update source table:

UPDATE c
SET LineReference = STUFF((SELECT DISTINCT  ','+CAST(f.LineReference as nvarchar(10))
        FROM final f
        WHERE c.LineReference = f.LineReferenceOld
        FOR XML PATH('')),1,1,'')
FROM @BillsRefs c