SA0254 : Invalid operation due to cursor closed or not declared

Improper cursor usage in T-SQL code, such as not declaring or opening the cursor before use, can lead to runtime errors in SQL Server.

Description

In SQL Server, a cursor is a database object used to retrieve, manipulate, and navigate through result sets row by row. However, improper use can lead to errors if the cursor is not properly declared or opened before use.

For example:

SQL
Copy
1-- Problematic use of a cursor without declaration or opening
2FETCH NEXT FROM MyCursor;

In this example, attempting to fetch from MyCursor without ensuring it is declared and opened can lead to an error, as SQL Server requires cursors to be in a specific state before operations can be performed on them.

  • This can result in runtime errors if a cursor is referenced without being declared.

  • Using a cursor that has not been opened will also cause the SQL Server to throw an error.

How to fix

Ensure the proper declaration and opening of cursors to prevent runtime errors in SQL Server.

Follow these steps to address the issue:

  1. Declare the cursor using the DECLARE statement, specifying the cursor name and the query that the cursor will navigate. For example:

  2. Open the cursor using the OPEN statement before fetching any data from it. This step is crucial to put the cursor in a usable state.

  3. Use the FETCH statement to retrieve rows from the result set referenced by the cursor.

  4. Finally, ensure to close the cursor using the CLOSE statement and, if necessary, deallocate the cursor using the DEALLOCATE statement to release resources.

For example:

SQL
Copy
 1-- Correct use of a cursor
 2DECLARE MyCursor CURSOR FOR
 3SELECT Column1, Column2 FROM TableName;
 4
 5OPEN MyCursor;
 6
 7FETCH NEXT FROM MyCursor;
 8
 9-- Continue processing rows
10
11CLOSE MyCursor;
12DEALLOCATE MyCursor;

Scope

The rule has a Batch scope and is applied only on the SQL script.

Parameters

Rule has no parameters.

Remarks

The rule does not need Analysis Context or SQL Connection.

Effort To Fix
13 minutes per issue.
Categories

Design Rules, Bugs

Additional Information
Example Test SQL
SQL
Copy
 1DECLARE sample_cursor CURSOR FOR 
 2SELECT Name FROM sys.databases;
 3
 4-- Attempt to fetch without opening the cursor
 5FETCH NEXT FROM sample_cursor;
 6
 7-- Proper cursor usage
 8OPEN sample_cursor;
 9FETCH NEXT FROM sample_cursor;
10CLOSE sample_cursor;
11
12-- Invalid operation: Closing before fetching
13OPEN sample_cursor;
14CLOSE sample_cursor;
15FETCH NEXT FROM sample_cursor;
16
17DEALLOCATE sample_cursor;
18
19DECLARE test_cursor CURSOR FOR 
20SELECT name FROM sys.objects WHERE type = 'U';
21
22OPEN test_cursor;
23FETCH NEXT FROM test_cursor;
24DEALLOCATE test_cursor;
25
26-- Error: Fetching after deallocation
27FETCH NEXT FROM test_cursor;
Analysis Results
  Message Line Column
1 SA0254 : The referenced cursor [sample_cursor] is not opened. 5 16
2 SA0254 : The referenced cursor [sample_cursor] is closed earlier. 15 16
3 SA0254 : The referenced cursor [test_cursor] is deallocated earlier. 27 16
See Also

Other Resources

Analysis Rules