How to Dynamically Create a Cursor in MySQL Stored Procedures скачать в хорошем качестве

How to Dynamically Create a Cursor in MySQL Stored Procedures

Learn how to pass a table name as a parameter in MySQL stored procedures and execute dynamic SQL to avoid common errors. --- This video is based on the question https://stackoverflow.com/q/62360722/ asked by the user 'Ubuntu Tricks' ( https://stackoverflow.com/u/8626498/ ) and on the answer https://stackoverflow.com/a/62360838/ provided by the user 'GMB' ( https://stackoverflow.com/u/10676716/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: MySQL:creating cursor dynamically in procedure Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- How to Dynamically Create a Cursor in MySQL Stored Procedures When working with MySQL stored procedures, one common issue developers face is dynamically handling table names within their procedures. You may be looking to transfer data from one table to another using procedures, but you encounter an error when trying to utilize the table name as a parameter. In this post, we'll explore how to address this problem effectively using dynamic SQL instead of cursors. Understanding the Problem Consider a situation where you have written a stored procedure designed to copy all records from a table to another. You want to pass the table name as a parameter but end up running into an error when invoking the procedure. The following is a typical error message you might receive: [[See Video to Reveal this Text or Code Snippet]] This error arises because SQL does not allow you to directly use a variable as a table name in your queries. Let's dive into how to resolve this problem. Solution: Using Dynamic SQL Instead of trying to use a cursor, the recommended approach is to leverage dynamic SQL. This method allows you to build your SQL statement as a string and then execute it. The following sections outline the changes needed to your original procedure. Revised Procedure Here’s an example of how to implement the changes using the PREPARE statement for dynamic SQL execution: [[See Video to Reveal this Text or Code Snippet]] Key Components of the Revised Code Parameter Declaration: The procedure takes two parameters: p_company_name, which is the name of the table, and p_sn_f, representing a serial number or identifier. Dynamic SQL Creation: The SET @ sql statement constructs your SQL query. The CONCAT() function combines static strings with the dynamic p_company_name. Note that ? is used as a placeholder for the p_sn_f value. Executing the SQL Statement: Use PREPARE to prepare the SQL statement for execution. The EXECUTE statement runs the prepared SQL with the specified parameters. Finally, the DEALLOCATE PREPARE command cleans up and frees the resources associated with the prepared statement. Conclusion By adopting dynamic SQL, you can easily resolve the issue of using table names as parameters in your stored procedures. This method not only circumvents the limitations of cursors in this context but also aligns with SQL's set-based philosophy. You can efficiently transfer data from one table to another using the revised procedure without running into errors about nonexistent tables. Now that you've learned how to solve the problem of dynamic cursor creation in MySQL, you should find similar scenarios much more manageable. Happy coding!