Stored procedures in mysql

MySQL is a commonly used relational database, in which stored procedures are a very important feature. Stored procedure is an advanced application of SQL language. It combines multiple SQL statements and processes them as a unit to achieve complex operations on the database.

Introduction to stored procedures

A stored procedure is one of the database objects, the same as tables, views, indexes, etc. It is a set of predefined SQL statements. In MySQL, a stored procedure is a reusable program code that can be executed on the client or on the database server.

Characteristics of stored procedures:

1. Encapsulation

Stored procedures can combine a set of SQL statements into one function, improving the encapsulation and security of the database. , to avoid some improper operations.

2. High execution efficiency

The stored procedure is compiled into binary code when it is created. When executed, the binary code is directly called, and the execution efficiency is very high.

3. Reusability

The stored procedure can be called multiple times, increasing reusability.

4. Powerful function

Stored procedure is an advanced application of SQL language. It is very powerful and can realize complex operations of the database.

Syntax of stored procedures

Definition of stored procedures

The definition syntax of stored procedures is as follows:

CREATE PROCEDURE procedure_name([parameter list])
BEGIN

存储过程主体内容

END;

Among them, [Parameter List] is optional and represents the input and output parameters required by the stored procedure. The main content of the stored procedure is a set of SQL statements, which can include control flow statements (such as IF, WHILE and LOOP, etc.), and can also call other stored procedures.

Stored procedure parameters

Stored procedures can have input parameters, output parameters and input/output parameters. Input parameters are values ​​passed in from the outside and are used in the stored procedure. Output parameters are calculated or assigned in the stored procedure and returned to the caller after the stored procedure is executed. Input/output parameters are used for bidirectional communication.

The stored procedure parameter syntax is as follows:

CREATE PROCEDURE procedure_name(IN|OUT|INOUT parameter_name parameter_type[,IN|OUT|INOUT parameter_name parameter_type...])
BEGIN

存储过程主体内容

END;

Among them, parameter_name is the parameter name, parameter_type is the parameter type, IN represents the input parameter, OUT represents the output parameter, and INOUT represents the input/output parameter.

Stored procedure call

The stored procedure call syntax is as follows:

CALL procedure_name([parameter list])

Among them, procedure_name is the name of the stored procedure, and the parameters Lists are input parameters required by the stored procedure.

Stored Procedure Example

The following is a simple stored procedure creation example. It creates a stored procedure named getUserInfo, which requires the user name to be entered and returns the user's nickname:

DELIMITER $$
CREATE PROCEDURE getUserInfo(IN name VARCHAR(20), OUT nickname VARCHAR(20))
BEGIN

SELECT user_nickname INTO nickname FROM user WHERE user_name=name;

END $$
DELIMITER ;

This stored procedure has two parameters: name is an input parameter, indicating the user name of the query; nickname is an output parameter, indicating the user's nickname. The main content of the stored procedure is a SELECT statement, which queries the user table for qualified user nicknames and assigns them to nickname.

Stored procedure call:

CALL getUserInfo('jack', @nickname);
SELECT @nickname;

The above code will call the getUserInfo stored procedure, the parameters are 'jack' assigns the query result to the @nickname variable and outputs the @nickname variable.

Summary of stored procedures

Stored procedures are an important feature of MySQL, which can help us better implement database operations. Through stored procedures, we can combine multiple SQL statements into a unit to improve operation encapsulation and security. It also improves query efficiency, increases reusability and scalability. In practical applications, stored procedures can be used to handle some complex business requirements, such as data import, data conversion, calculation, etc. Compared with traditional SQL statements, stored procedures are more convenient and reliable, and are an indispensable part of database development.

The above is the detailed content of Stored procedures in mysql. For more information, please follow other related articles on the PHP Chinese website!