How to Correctly Pass Expression Results as Stored Procedure Parameters?

SQL Server Stored Procedure Parameter Pitfalls: Handling Expression Results

Passing the output of expressions or function calls directly as parameters in SQL Server stored procedures often leads to errors. Let's illustrate this with a common issue encountered in SQL Server 2005:

The following code snippet generates a syntax error:

<code class="language-sql">DECLARE @pID int;
SET @pID = 1;
EXEC WriteLog 'Component', 'Source', 'Could not find given id: ' + CAST(@pID AS varchar);</code>

This results in the error:

<code>Msg 102, Level 15, State 1, Line 4
Incorrect syntax near '+'.</code>

The root cause? SQL Server doesn't allow direct use of expressions or function results within the stored procedure's parameter list. The solution involves an intermediate variable.

Here's the corrected approach:

<code class="language-sql">DECLARE @pID INT;
DECLARE @logMessage VARCHAR(50);

SET @pID = 1;
SET @logMessage = 'Could not find given id: ' + CAST(@pID AS VARCHAR(11));
EXEC WriteLog 'Component', 'Source', @logMessage;</code>

This revised code assigns the expression's result to @logMessage, which is then correctly recognized as the third parameter. The stored procedure executes without errors.

It's crucial to note: This restriction applies solely to parameter values; expressions within the stored procedure's body are unaffected.

The above is the detailed content of How to Correctly Pass Expression Results as Stored Procedure Parameters?. For more information, please follow other related articles on the PHP Chinese website!