Question

Suppose you have a table like this:

ID     FNAME      LNAME
1      Bob        Smith
2      Sally      Jones

A simple SELECT * FROM [Table] will return all rows. But what if you wanted to build a single string out of the results, and the column names are unknown? In other words, this will not work:

SELECT ID + ',' + FNAME + ',' + LNAME FROM [Table]

because you don’t know the column names. Additionally, COALESCE won’t work because it doesn’t accept wildcards. Ideally you want to execute something like this:

SELECT dbo.FunctionThatSplitsResultsToString(*) FROM [Table]

and have it return

1,Bob,Smith
2,Sally,Jones

Is this possible?

Answer 1

This is a corrected version of the answer @Igor gave. In addition to concatenating comma characters between the values, it converts NULL values to an empty string (because concatenating a string to NULL results in a NULL value).

DECLARE @sql NVARCHAR(max)='SELECT '
DECLARE @TableName NVARCHAR(max) = 'Table_Name' -- <-- Set the target table name here

SELECT @sql=@sql+N'ISNULL(CAST(' + name +' as NVARCHAR(max)), '''')+'',''+'
FROM sys.columns
WHERE object_id=OBJECT_ID(@TableName)

SELECT @sql=SUBSTRING(@sql,1,LEN(@sql)-5)+N' FROM ' + @TableName
--SELECT @sql -- uncomment to see the query string

EXEC sp_executesql @sql