How to fix Error 8402 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 8402 – Invalid Data Type in Statement

Why This Error Happens

Error 8402 occurs when a Transact-SQL statement references a column, variable, or parameter with a data type that is not supported by the specific clause or operation being executed, such as using text, ntext, image, or xml types in contexts that require simpler scalar types. This is commonly triggered when legacy data types are used in newer T-SQL constructs like MERGE, table-valued parameters, or certain system procedures that explicitly restrict allowed types. It can also surface after a database migration or compatibility level upgrade to SQL Server 2025, where deprecated types that worked under older compatibility levels are no longer tolerated in specific statements.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Statement and Column

  • Review the full error message to capture the exact column name and statement type referenced in the ‘%S_MSG’ placeholders.
  • Run sp_help 'YourTableName' in SQL Server Management Studio (SSMS) to inspect the current data type of the flagged column.
  • Check if the column uses a deprecated type like text, ntext, image, or timestamp instead of modern equivalents.

Step 2: Convert the Column to a Supported Data Type

  • Alter the column to use a supported type, for example: ALTER TABLE YourTable ALTER COLUMN YourColumn VARCHAR(MAX);
  • For text/ntext/image types, migrate to VARCHAR(MAX), NVARCHAR(MAX), or VARBINARY(MAX) respectively.
  • If the column is used in a MERGE statement, ensure it is not a computed column with an unsupported base type.

Step 3: Check Database Compatibility Level

  • Open SSMS, right-click the database, select Properties, then navigate to the Options page.
  • Confirm the Compatibility Level is set to 170 (SQL Server 2025) under ALTER DATABASE YourDB SET COMPATIBILITY_LEVEL = 170;
  • Lower compatibility levels can mask or alter how certain data type restrictions are enforced, so ensure consistency with the engine version.

Step 4: Review Stored Procedures and Table-Valued Parameters

  • If the error originates from a table-valued parameter (TVP), run sp_help 'YourTVPTypeName' to check the column definitions inside the type.
  • Recreate the TVP type with supported data types using CREATE TYPE YourTVPTypeName AS TABLE (Column1 INT, Column2 NVARCHAR(100));
  • Update any stored procedures or application code referencing the old TVP structure to match the corrected schema.

Step 5: Apply Latest Cumulative Update

  • On Windows Server 2025 or Windows 11, open PowerShell as Administrator and check your current SQL Server build with SELECT @@VERSION;
  • Download and install the latest Cumulative Update (CU) for SQL Server 2025 from the Microsoft Update Catalog to resolve any known data type validation bugs.
  • Restart the SQL Server service via services.msc or Restart-Service -Name 'MSSQLSERVER' after installation.

Alternative or Verification Steps

  • Re-run the original query or application transaction that triggered Error 8402 and confirm it completes without raising the same error in SSMS or the Windows Event Viewer.
  • If the issue persists, use sys.columns and sys.types system views to cross-reference every column involved in the statement and confirm none still reference deprecated or unsupported data types.