If you want to concatenate every row value separated by comma, use these methods:
1. Use Variable to Concatenate
declare @sql varchar(8000)
In the above T-SQL code, each row value is concatenated with the variable @sql
2. Use FOR XML clause to Concatenate
stuff((select distinct top 100 percent ',' + data from @t as t for xml path('')), 1, 1, '')
from @t as t
In the above example, FOR XML clause is used to concatenate row values. Since a comma is used, the query concatenates values separated by comma.