Скачать или смотреть How to Use STUFF FOR XML PATH to Combine Rows in SQL

Learn how to effectively combine multiple rows into a single column in SQL Server using the `STUFF FOR XML PATH` method, providing a clear example and solution.
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Combining Multiple Rows into a Single Column in SQL Server

If you've ever worked with SQL Server, you've likely encountered the challenge of needing to combine multiple rows of data into a single column. This is a common requirement, especially when presenting data in a more readable format. One such solution involves the use of the STUFF FOR XML PATH method. In this guide, we'll explore how to achieve this with a practical example.

The Problem

Let's say you have a table with the following structure:

Num1Type1Type2AcctInd1X2XXXCA111ERROR1X2XXXCA222ERRORX22XXXCA111ERRORX22XXXCA222ERRORX22XXXCA333ERRORX22XXXCA444ERRORYou want to add a new column, Acct_List, that combines all the Acct values associated with each unique combination of Num1, Type1, and Type2. The desired result would look like this:

Num1Type1Type2AcctIndAcct_List1X2XXXCA111ERROR111, 2221X2XXXCA222ERROR111, 222X22XXXCA111ERROR111, 222, 333, 444X22XXXCA222ERROR111, 222, 333, 444X22XXXCA333ERROR111, 222, 333, 444X22XXXCA444ERROR111, 222, 333, 444The Solution

To achieve this, you can use the SQL function STUFF in conjunction with FOR XML PATH. Here’s how:

Step-by-Step Explanation

Basic Syntax:
The basic structure for the SQL query involves using a subquery with FOR XML PATH('') to concatenate string values.

Main Query:
Within your main query, you need to define how to conditionally combine the account numbers.

Using the WHERE Clause:
It's crucial to include conditions that allow you to match the appropriate Num1 values for the concatenation.

The Correct SQL Query

Here's how the final SQL query should look:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Query:

Subquery with FOR XML PATH:

This section creates a comma-separated string of Acct values for unique combinations identified by Num1.

Conditional Matching:

The WHERE t1.Num1 = t2.Num1 line ensures that only the accounts belonging to the same Num1 are concatenated.

String Manipulation with STUFF:

The STUFF function removes the leading comma and space from the resulting string.

Example Output

By running the above query, your output would now contain the desired aggregated column Acct_List, properly formatted for each unique combination.

Conclusion

Combining multiple rows into a single column can significantly enhance the readability of reports and data presentations in SQL Server. By mastering the use of STUFF FOR XML PATH, you'll empower yourself to create more informative datasets that suit your analysis needs.

Feel free to experiment with this query in your SQL environment. Happy querying!