SA0258 : The number of FETCH statement variables does not match the number of columns in the cursor definition

Ensuring the number of columns in a cursor’s SELECT list matches the number of variables in the FETCHINTO clause is essential to prevent runtime errors and unexpected behavior.

Description

A common issue in T-SQL scripts involves mismatches between the number of columns in a cursor’s SELECT list and the number of variables in the INTO clause of a FETCH statement. This mismatch can cause runtime errors or unintended behavior in SQL Server.

For example:

SQL
Copy
1-- Example of problematic FETCH statement
2DECLARE cur CURSOR FOR
3SELECT FirstName, LastName FROM Employees;
4
5OPEN cur;
6FETCH NEXT FROM cur INTO @Name;

In this example, the FETCH statement attempts to place values from two columns into a single variable, resulting in an imbalance. This inconsistency can lead to errors, such as data loss or incorrect values being stored in variables, which can further complicate your data processing tasks.

  • Incorrect number of variables leads to runtime errors preventing code execution.

  • Mismatched assignments might lead to data inconsistencies and logical errors.

How to fix

Ensure each column in the cursor’s SELECT list matches a corresponding local variable in the FETCH INTO clause to avoid mismatches and runtime errors.

Follow these steps to address the issue:

  1. Examine the SELECT list in the cursor declaration to count the columns being selected.

  2. Verify the INTO clause in the FETCH statement to ensure the number of variables matches the number of columns. Each column should correspond to a unique variable.

  3. Adjust the INTO list or the SELECT list to correct any discrepancies. Add or remove variables as necessary to achieve one-to-one correspondence.

  4. Test the modified cursor to confirm that it now operates without errors and behaves as expected.

For example:

SQL
Copy
1-- Corrected example of FETCH statement
2DECLARE cur CURSOR FOR 
3SELECT FirstName, LastName FROM Employees;
4OPEN cur;
5FETCH NEXT FROM cur INTO @FirstName, @LastName;

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 @col1 int, @col2 int, @col3 int
 2DECLARE test1 CURSOR
 3    FOR SELECT col1,col2,col3 FROM Table1
 4
 5OPEN test1
 6FETCH NEXT FROM test1
 7 INTO @col1, @col2
 8
 9FETCH NEXT FROM test1
10 INTO @col1, @col2, @col3
11
12DECLARE test2 CURSOR
13    FOR SELECT col1,col2,col3, 4 FROM Table1 t 
14        UNION ALL
15        SELECT 1, 2, 3, 4 FROM Table1 t 
16OPEN test2
17FETCH NEXT FROM test2
18 INTO @col1, @col2,@col3
19
20DECLARE test3 CURSOR
21    FOR SELECT col1,col2,col3,t.* FROM Table1 t 
22        UNION ALL
23        SELECT 1, 2, 3, t.* FROM Table1 t 
24OPEN test3
25FETCH NEXT FROM test3
26 INTO @col1, @col2,@col3
Analysis Results
  Message Line Column
1 SA0258 : The number of FETCH statement variables is 2, while the number of columns in the cursor definition is 3. 7 1
2 SA0258 : The number of FETCH statement variables is 3, while the number of columns in the cursor definition is 4. 18 1
See Also

Other Resources

Analysis Rules