How to fix Error 9313 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 9313

Why This Error Happens

This error occurs when SQL Server 2025 parses an XML attribute constructor within a FOR XML query (or XQuery expression) that contains more than one expression, or an expression combined with literal string values, inside a single attribute value. The SQL Server XML parsing engine requires attribute constructors to resolve to a single, unambiguous expression value rather than a concatenated mix of variables, columns, and strings. This typically surfaces after a migration or upgrade when legacy T-SQL code containing non-compliant XQuery syntax is executed against the newer SQL Server 2025 engine, which enforces stricter XML standards compliance than previous versions.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Query

  • Capture the exact T-SQL statement that triggered Error 9313 using SQL Server Profiler or Extended Events (xml_deadlock_report won’t help here—use a generic error event filter on Error Number 9313).
  • Review the query for FOR XML PATH or FOR XML EXPLICIT clauses, specifically looking at attribute definitions written like @attr = col1 + '-' + col2.
  • Check any recently migrated stored procedures located in your database’s Programmability > Stored Procedures node in SQL Server Management Studio (SSMS) 21.

Step 2: Rewrite the Attribute Constructor Using CONCAT()

  • Replace mixed string/expression concatenation inside the attribute constructor with the CONCAT() function so only a single resolved expression is passed.
  • Example fix: change SELECT col1 + '_' + col2 AS "@AttributeName" FOR XML PATH('Root') to SELECT CONCAT(col1, '_', col2) AS "@AttributeName" FOR XML PATH('Root').
  • Alternatively, pre-calculate the concatenated value in a derived table or Common Table Expression (CTE) before passing it into the FOR XML clause.

Step 3: Update Compatibility Level Settings

  • Open SSMS and connect to the instance, then navigate to Database Properties > Options > Compatibility Level.
  • Confirm the database is not unintentionally running under an older compatibility level (e.g., 150 or 160) that may interact unexpectedly with the new XML parser; set it to 170 for full SQL Server 2025 engine behavior using: ALTER DATABASE [YourDB] SET COMPATIBILITY_LEVEL = 170;
  • Restart the SQL Server service via Services.msc on Windows Server 2025 if the setting does not immediately take effect.

Step 4: Validate XML Schema Collections

  • If the attribute constructor is tied to a typed XML column, check the associated XML Schema Collection for outdated constraints using SELECT * FROM sys.xml_schema_collections;.
  • Drop and recreate the schema collection if it references deprecated attribute typing rules from earlier SQL Server versions.

Alternative or Verification Steps

  • Re-run the corrected query in SSMS and confirm the XML output generates successfully without Error 9313, then check the Windows Event Viewer (Applications and Services Logs > MSSQLSERVER) to confirm no recurrence.
  • If the error persists on complex nested queries, isolate the FOR XML clause into a standalone temporary stored procedure to test the CONCAT() fix in isolation before merging it back into the production codebase.