Eliminating MySQL Error 1329: Resolving Duplicate Parameter Issues in Stored Procedures

MySQL Error 1329 – SQLSTATE: 42000 (ER_SP_DUP_PARAM) occurs when a stored procedure or function is defined with parameters that have duplicate names. The error message “Duplicate parameter: %s” indicates that there is more than one parameter with the same name, which is not allowed in MySQL stored routine definitions.

Understanding the Error

When creating or altering stored procedures or functions in MySQL, each parameter must have a unique name. This error is triggered during the creation or alteration of a stored routine if the same parameter name is used more than once in the parameter list.

Diagnosing the Problem

To address this error, examine the stored procedure or function definition:

  1. Review Parameter Names: Look at the names of all parameters in the routine definition to identify any duplicates.
  2. Check for Typos: Sometimes, a simple typo can result in a parameter being named twice.

Fixing the Error

Here’s how to correct Error 1329 by ensuring all parameters have distinct names:

  1. Correcting Duplicate Names: CREATE PROCEDURE add_employee( IN employee_name VARCHAR(100), IN employee_age INT, IN employee_department VARCHAR(100) ) BEGIN -- Procedure body END; In this example, all parameters have unique names, which is the correct approach.
  2. Renaming Parameters to Avoid Conflicts: CREATE FUNCTION calculate_salary( IN base_salary DECIMAL(10,2), IN bonus DECIMAL(10,2), IN deduction DECIMAL(10,2) ) RETURNS DECIMAL(10,2) BEGIN DECLARE total_salary DECIMAL(10,2); SET total_salary = base_salary + bonus - deduction; RETURN total_salary; END; Here, each parameter has a distinct name, ensuring there are no duplicates.
  3. Avoiding Common Typos:
    sql CREATE PROCEDURE update_employee_status( IN emp_id INT, IN new_status VARCHAR(50) ) BEGIN UPDATE employees SET status = new_status WHERE id = emp_id; END;
    Double-check parameter names like emp_id and new_status to ensure they are not mistakenly repeated.


  • Use clear and descriptive names for parameters to reduce the chance of duplication.
  • Consistently follow a naming convention for parameters to help distinguish them.
  • Always review your stored routine definitions before executing them to catch any errors early.
  • Test your stored procedures and functions after making changes to ensure they work as expected.

By carefully naming parameters and reviewing your stored routine definitions for any duplicates, you can prevent MySQL Error 1329 and maintain clean and functional stored procedures and functions.

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