How Can I Replicate MySQL's group_concat Function in SQL Server 2005?

Replicating MySQL's group_concat in SQL Server 2005 using a User-Defined Function

MySQL's group_concat function efficiently concatenates values from multiple rows into a single string. SQL Server 2005 lacks this built-in function, creating challenges when migrating applications. This article demonstrates how to create a user-defined function (UDF) in SQL Server 2005 to achieve similar results.

The UDF approach allows for custom logic to extend SQL Server's functionality. The function takes necessary parameters, performs the concatenation, and returns the combined string. Here's a sample UDF:

<code class="language-sql">CREATE FUNCTION dbo.my_group_concat (@field NVARCHAR(MAX), @delimiter NVARCHAR(1) = ',')
RETURNS NVARCHAR(MAX)
AS
BEGIN
    DECLARE @result NVARCHAR(MAX) = '';
    DECLARE @row_num INT = 0;

    WHILE @row_num  0
            SET @result += @delimiter;
        SET @row_num += 1;
    END;
    RETURN @result;
END;</code>

This function can be used in queries to mimic group_concat behavior:

<code class="language-sql">SELECT 
    empName, dbo.my_group_concat(projID, ' / ') AS concatenated_projID
FROM 
    project_members 
GROUP BY 
    empName;</code>

This query produces output similar to group_concat:

<code>empName | concatenated_projID
--------|----------------------
ANDY    | A100 / B391 / X010
TOM     | A100 / A510</code>

Important Note: This UDF provides a functional equivalent, but it's not a perfect replica of MySQL's group_concat. Performance considerations may also differ. This solution offers a practical workaround for migrating applications requiring this specific functionality.

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