MySQL stored procedure

One 、 Introduction to stored procedures

         A stored procedure is a set of functions to accomplish SQL Statement set .MySQL 5.0 Finally started to support stored procedures , It is the most important function in the database , Use common or complex work in advance SQL The statement is written and stored with a specified name , This process is compiled and optimized and stored in the database server , So it's called a stored procedure .

        Why use stored procedures ：

• encapsulation ： After the stored procedure is created , Can be called multiple times in a program , Without having to rewrite the stored procedure's SQL sentence , And database professionals can modify stored procedures at any time , It doesn't affect the application source code that calls it .
• Can be enhanced SQL The function and flexibility of statements ： Stored procedures can be written with process control statements , Very flexible , It can complete complex judgment and more complex operation .
• Can reduce network traffic ： Because stored procedures run on the server side , And fast execution , So when the stored procedure is called on the client computer , All that's passed in the network is the call statement , This reduces network load .
• High performance ： After the stored procedure is executed once , The generated binary code resides in the buffer , In later calls , Just execute the binary code from the buffer , So it improves the efficiency and performance of the system .
• Improve database security and data integrity ： Using stored procedures can complete all database operations , And can control the access right of database information by programming .

Two 、MySQL Create stored procedure

Syntax and parameters

grammar ：

CREATE PROCEDURE  Process name ([proc_parameter[,...]])
 [characteristic ...] routine_body 

explain

proc_parameter ： Express  [ IN | OUT | INOUT ] param_name type

• IN Input parameters ： Indicates that the caller passes a value... To the procedure
• OUT Output parameters ： Indicates that the procedure passes out a value to the caller
• INOUT Input/output parameter ： It means that the caller passes in a value to the procedure , It also indicates that the procedure passes out a value to the caller

type ： Indicates any valid MySQL data type 
characteristic : Express  
 LANGUAGE SQL
 | [NOT] DETERMINISTIC
 | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
 | SQL SECURITY { DEFINER | INVOKER }
 | COMMENT 'string'
routine_body  Means effective SQL Procedure statement or statement   finger :“ The process of body ”

1. NOT DETERMINISTIC ： If a program or thread always produces the same result for the same input parameter , It is considered to be “ affirmatory ”, Otherwise, it would be “ Not sure ” Of . If neither is given DETERMINISTIC There is no given NOT DETERMINISTIC, The default is NOT DETERMINISTIC.
2. CONTAINS SQL ： A statement indicating that a subroutine does not contain read or write data , The default is CONTAINS SQL
3. NO SQL Indicates that the subroutine does not contain SQL sentence
4. READS SQL DATA Indicates that the subroutine contains statements that read data , But it doesn't include statements that write data
5. MODIFIES SQL DATA Indicates that the subroutine contains statements that write data
6. SQL SECURITY Features can be used to specify The subroutine should be executed with the permission of the creator of the subroutine , Or use the caller's permission to execute . The default value is DEFINER. stay SQL:2003 The middle is a new feature . The creator or caller must be accessed by License of the database associated with the subroutine . stay MySQL 5.1 in , There has to be EXECUTE Permission to execute subroutines . The user who must have this permission is either the definer , Or the caller , It depends. SQL SECURITY How the feature is set .

         To be in MySQL 5.1 Create a stored program in , Must possess CREATE ROUTINE jurisdiction , also ALTER ROUTINE and EXECUTE Permission is automatically granted to its Creator .

         By default , Subroutines are associated with the current database . To explicitly associate a subroutine with a given database , You can specify the name of the subroutine when you create it db_name.sp_name.

in、out、inout Use

1、 Parameterless stored procedure

/* Create a parameterless stored procedure  */
DELIMITER $$
CREATE PROCEDURE p_student() #  Declaring stored procedures 
 BEGIN #  Stored procedure start symbol 
 SELECT * FROM student;
 END$$ # Stored procedure end symbol 
DELIMITER $$ #  Declaration statement Terminator   You can also use DELIMITER // 

#  Calling stored procedure 
call p_student

 

2、in Parameter stored procedures

/*in  Stored procedure for input parameters   Input id The line of the query */
DELIMITER $$
CREATE PROCEDURE p_student2(IN stu_num INT)
BEGIN
 SELECT * FROM student WHERE num = stu_num;
END$$
DELIMITER $$

#  Calling stored procedure 
call p_student2(2);

3、out Parameter stored procedure description

/*out  Stored procedure */
DELIMITER $$
CREATE PROCEDURE p_student3(OUT stu_name VARCHAR(20))
 BEGIN
 SELECT NAME INTO stu_name FROM student WHERE num=2;
 END$$
 DELIMITER $$

#  Calling stored procedure   Store the result of execution in @name in 
call p_student3(@name);
#  Inquire about @name
select @name

 4、inout Parameter stored procedure description

/*inout Stored procedure */
DELIMITER$$
CREATE PROCEDURE p_student4(INOUT stu_name VARCHAR(20))
BEGIN
 SELECT NAME INTO stu_name FROM student WHERE name=stu_name;
END$$
DELIMITER $$

#  Set up  @name Value 
set @name=' Zhang San ';
#  take  @name Pass in and return the result 
call p_student4(@name);
#  The result returned by the query 
select @name