Converting Comma Separated Value to Rows and Vice Versa in SQL Server

Query 1: 

Using ->> COALESCE function

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DECLARE @temp VARCHAR(MAX)

SELECT @temp = COALESCE(@temp+', ' ,'') + '['+ Columnname+ ']'

FROM [dbo].[mstCombobox_T] where Flag=33 order by SNo

SELECT @temp

// Result  

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]

Query 2: 

Using without ->> COALESCE function

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DECLARE @temp VARCHAR(MAX)

SET @temp = ''

SELECT @temp = @temp + state + ', '

FROM [dbo].[mstCombobox_T] where Flag=33 order by SNo

SELECT SUBSTRING(@temp, 0, LEN(@temp))

// Result  

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]

Query 3:

Using ->> FOR XML PATH

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DECLARE @temp VARCHAR(MAX)

SET @temp = (SELECT ', ' + cast(s.state as varchar)

                      FROM [dbo].[mstCombobox_T] s where Flag=33 order by SNo

                      ORDER BY s.state

                     FOR XML PATH(''))

SELECT SUBSTRING(@temp, 2, 200000) AS state

// Result 

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]