Summary of MySQL stored procedure in, out, inout parameter examples

mysql video tutorialThe column introduces the in, out, and inout parameters of MySQL stored procedures

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• Stored Procedure
• • 1. Create a stored procedure and view global variables
  • 2. Changes in global variable values ​​when calling stored procedures

Stored Procedure

1. Create a stored procedure and view global variables

mysql> create database yy;Query OK, 1 row affected (0.00 sec)mysql> use yy;Database changed
mysql> set @num1=10,@num2=20,@num3=30;	//设置全局变量mysql> delimiter $$
mysql> create procedure p(in num1 int,out num2 int,inout num3 int)
    -> begin    -> select num1,num2,num3;
    -> set num1=100,num2=200,num3=300;
    -> select num1,num2,num3;
    -> end $$
Query OK, 0 rows affected (0.00 sec)mysql> delimiter ;mysql> call p(@num1,@num2,@num3);

Summary 1:

• The in and inout parameters will pass the value of the global variable into the stored procedure, while the out parameter will not pass the value of the global variable into the stored procedure. When using a stored procedure, the parameter values ​​in, out, and inout will all change.

2. Changes in global variable values ​​when calling stored procedures

mysql> select @num1,@num2,@num3;

Summary 2:

• After calling the stored procedure, it is found that the in parameter will not change the value of the global variable, but the out and inout parameters will change the value of the global variable after calling the stored procedure, and the stored procedure will be changed. The value after the procedure reference is assigned to the global variable.
• The in parameter assignment type can be a variable or a fixed value, while the out and inout parameter assignment types must be variables.

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