Mysql query stored procedure

MySQL is a commonly used database system that provides the function of stored procedures, which allows users to package a series of SQL statements for multiple executions. MySQL's stored procedure function can easily manage and operate data.

A stored procedure is a precompiled SQL statement that is stored in the database in the form of a program and can be called when needed. Stored procedures can accept parameters and return results. Its advantages include increased application security, data consistency, and code reuse.

Syntax of stored procedure

The syntax of stored procedure is as follows:

DELIMITER //

CREATE PROCEDURE procedure_name([IN/OUT] parameter_name data_type)

BEGIN

--SQL statements

END //

DELIMITER ;

Statement explanation:

• DELIMITER: Specify the delimiter, the default is semicolon ";".
• CREATE PROCEDURE: Keyword to create a stored procedure.
• procedure_name: The name of the stored procedure.
• IN/OUT: Define the parameters passed to the stored procedure. IN means passing parameters to the stored procedure, and OUT means returning parameter values ​​from the stored procedure.
• parameter_name: The name of the parameter.
• data_type: The data type of the parameter.
• BEGIN: The starting position of the stored procedure.
• END: The end position of the stored procedure.

Creation of stored procedures

The following is an example of creating a stored procedure:

DELIMITER //

CREATE PROCEDURE get_employee(IN employee_id INT, OUT employee_name VARCHAR(50))
BEGIN

SELECT name INTO employee_name FROM employees WHERE id = employee_id;

END //

DELIMITER ;

The stored procedure is named "get_employee" , accepts an integer type parameter named "employee_id" and returns a string type parameter named "employee_name". The SQL statement in the stored procedure uses the SELECT statement to select the employee named "employee_id" from the "employees" table, and assigns his name to the "employee_name" parameter.

Execution of stored procedures

After the stored procedure is created, you can use the CALL statement to execute the stored procedure.

CALL get_employee(2, @employee_name);
SELECT @employee_name;

Call the "get_employee" stored procedure and pass the parameter "2" to the stored procedures. The stored procedure will return the employee name and store it in a variable called "@employee_name". Finally, use the SELECT statement to display the value of this variable.

Advantages of stored procedures

1. Reduce network traffic

Stored procedures are executed in the database, so they can reduce network traffic, thereby improving application Program performance. Through stored procedures, SQL statements that need to be executed multiple times can be packaged together, thereby reducing the number of network communications.

2. Reduce programming burden

Stored procedures encapsulate SQL statements in a program so that they can be reused when needed. This eases the programming burden because programmers do not have to write SQL statements for every application.

3. Improving security

Stored procedures can improve security because they allow the database administrator to control user access to the database. Stored procedures also enable programming language deficiencies to be bridged to better protect the database from cyberattacks.

4. Simplified maintenance

Stored procedures can make applications easier to maintain. If you need to modify a SQL statement, you only need to modify it in the stored procedure, without modifying each application that uses these SQL statements.

Conclusion

Stored procedures are a powerful feature of MySQL that can improve the performance, security, and maintainability of applications. Through stored procedures, multiple SQL statements can be packaged together and can accept parameters and return results. The use of stored procedures will greatly reduce the programming burden of applications and improve production efficiency.

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