Troubleshooting Guide: SQL Server Error 9331 (“Syntax error near ‘%ls'”)

Why This Error Happens

Error 9331 typically occurs when SQL Server’s parser encounters a malformed or unsupported T-SQL construct, often due to a JSON path expression, dynamic SQL string, or a Transact-SQL statement built using concatenated variables that produce invalid syntax at runtime. This is frequently triggered by mismatched quotes, incorrect use of newer SQL Server 2025 syntax features (such as JSON aggregate functions or vector search clauses), or a corrupted/truncated stored procedure definition caused by an incomplete deployment script. In some cases, encoding mismatches (e.g., Unicode vs. non-Unicode strings) in dynamically generated queries can also introduce invisible characters that the parser cannot interpret.

Step-by-Step Resolution Guide

Step 1: Isolate the Offending Statement

• Capture the exact query text from the error message, including the string following “near” — this identifies the token where parsing failed.
• Run the statement in isolation using SQL Server Management Studio (SSMS) 21 or Azure Data Studio connected to your SQL Server 2025 instance.
• Check for unbalanced brackets, missing commas, or unsupported keywords copied from older SQL Server syntax guides.

Step 2: Validate Dynamic SQL and JSON Syntax

• If the query uses sp_executesql or EXEC(), print the fully constructed SQL string to a variable and inspect it manually before execution:

DECLARE @debugSQL NVARCHAR(MAX) = @yourDynamicQuery;
PRINT @debugSQL;

• Confirm JSON functions (JSON_OBJECTAGG, JSON_ARRAYAGG, ISJSON) and any new SQL Server 2025 vector/AI query clauses follow the updated syntax documented in the 2025 Transact-SQL reference, as syntax changed from 2022/2019 versions.
• Replace smart quotes or non-standard Unicode characters (often introduced by copy-pasting from Word or PDFs) with standard ASCII quotes and parentheses.

Step 3: Check for Corrupted or Incomplete Object Definitions

• Navigate to the stored procedure, function, or view in SSMS Object Explorer, right-click, and select Modify to inspect the full definition.
• Run sp_helptext 'YourObjectName' from a query window to confirm the object wasn’t truncated during a prior deployment or script transfer.
• If corruption is suspected, redeploy the object from source control or your original .sql migration script located in your deployment pipeline directory (e.g., C:\Deployments\SQL2025\Scripts\).

Step 4: Review Compatibility Level Settings

• Open a query window and run:

SELECT name, compatibility_level FROM sys.databases WHERE name = 'YourDatabaseName';

• Ensure the database compatibility level is set to 170 (SQL Server 2025) if you intend to use newer syntax features; older compatibility levels may reject new keywords and cause parser errors.
• Update it if necessary:

ALTER DATABASE YourDatabaseName SET COMPATIBILITY_LEVEL = 170;

Alternative or Verification Steps

• Re-run the corrected query in a test environment and confirm it executes without returning Error 9331, then redeploy the fixed script to production during a maintenance window.
• If the error persists only in application-generated queries (not when run manually), enable SQL Server Profiler or Extended Events to capture the exact runtime-generated statement, as the application layer may be injecting malformed parameters.