Today, I encountered a situation where I needed to display all related data in a comma-separated list using a SELECT statement. Up until now, I have been using a scalar function that utilizes

COALESCE()

to achieve this. However, I discovered a fantastic solution that allows us to generate a comma-separated list without needing a scalar function. Let’s dive into it with SQLYoga guide.

Example Scenario

Consider the following table:

CREATE TABLE #test( field1 VARCHAR(5), field2 VARCHAR(5) );

Let’s insert some data into this table:

INSERT INTO #test SELECT '001','AAA' UNION ALL SELECT '001','BBB' UNION ALL SELECT '002','CCC' UNION ALL SELECT '003','DDD' UNION ALL SELECT '004','EEE' UNION ALL SELECT '004','FFF' UNION ALL SELECT '004','GGG'; Current Data in the Table

After inserting the data, our table looks like this:

Output: Show Output

Expected Output

We want to generate a comma-separated list of

field2

for each unique

field1

. The expected output is:

Output: Show Output

Proposed Solution

Here’s the SQL query to achieve the desired output:

SELECT field1, SUBSTRING( ( SELECT ', ' + field2 FROM #test t2 WHERE t1.field1 = t2.field1 ORDER BY t2.field2 FOR XML PATH('') ), 3, 1000) AS field2_list FROM #test t1 GROUP BY field1; Explanation

Subquery with

FOR XML PATH

: The subquery concatenates

field2

values into a single string separated by commas for each

field1

. The

FOR XML PATH('')

clause converts the result into XML format, which we then transform into a plain string.

Substring Function: The

SUBSTRING

function removes the leading comma and space from the concatenated string. The

3

indicates starting from the third character, effectively skipping the first two characters (

,

).

Group By: The

GROUP BY

clause ensures we get one row per

field1

.

Output

Running the above query will yield the following output:

Output: Show Output

With this approach, you can generate a comma-separated list without relying on scalar functions. This method is efficient and leverages SQL Server’s XML capabilities to concatenate strings.

Read More on SQLYoga about advanced SQL techniques and optimizing your queries.

At SQLYoga, we are committed to bringing you the latest and most efficient SQL Server solutions. This method of generating a comma-separated list is a prime example of how you can streamline your SQL queries and achieve better performance. Stay tuned for more tips and tricks to enhance your SQL skills and streamline your database management tasks.

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