Mysql存储过程入门

Summary: in this tutorial, we will show you step by step how to develop the first MySQL stored procedure by using CREATE PROCEDURE statement. In addition, we will show you how to call the stored procedures from SQL statements.

Writing the first MySQL stored procedure

We are going to develop a simple stored procedure named GetAllProducts() to help you get familiar with the syntax. The GetAllProducts() stored procedure selects all products from the products table.

Launch the mysql client tool and type the following commands:

DELIMITER //  CREATE PROCEDURE GetAllProducts() BEGIN    SELECT *  FROM products; END //  DELIMITER ;

Let’s examine the stored procedure in greater detail:

• The first command is DELIMITER //, which is not related to the stored procedure syntax. The DELIMITER statement changes the standard delimiter which is semicolon ( ;) to another. In this case, the delimiter is changed from the semicolon( ;) to double-slashes //. Why do we have to change the delimiter? Because we want to pass the  stored procedure to the server as a whole rather than letting mysql tool to interpret each statement at a time.  Following the END keyword, we use the delimiter // to indicate the end of the stored procedure. The last command ( DELIMITER;) changes the delimiter back to the standard one.

• We use the CREATE PROCEDURE statement to create a new stored procedure. We specify the name of stored procedure after the CREATE PROCEDURE statement. In this case, the name of the stored procedure is GetAllProducts. We put the parentheses after the name of the stored procedure.
  

• The section between BEGIN and END is called the body of the stored procedure. You put the declarative SQL statements in the body to handle business logic. In this stored procedure, we use a simple SELECT statement to query data from the productstable.

It’s kind of tedious to write the stored procedure in mysql client tool, especially when the stored procedure is complex. Most of the GUI tools for MySQL allow you to create new stored procedures via an intuitive interface.

For example, in MySQL Workbench, you can create a new stored procedure as follows:

Right mouse click on the Routines and choose “Create Procedure…”

Enter the stored procedure code and click the Apply button

You can review the code before MySQL stores it in the database. Click Apply button if everything is good.

MySQL compiles and puts the stored procedure in the database catalog; click the Finish button.

You can see a new stored procedure created under Routines of the classicmodelsdatabase

We have created a new stored procedure. Now, it’s time to learn how to use it.

Calling stored procedures

In order to call a stored procedure, you use the following SQL command:

CALL STORED_PROCEDURE_NAME()

You use the CALL statement to call a stored procedure e.g., to call the GetAllProducts stored procedure, you use the following statement:

CALL GetAllProducts();

If you execute the statement above, you will get all products in the products table.

In this tutorial, you have learned how to write a simple stored procedure by using the CREATE PROCEDURE statement and call it by using the CALL statement.

Related Tutorials

• MySQL Stored Procedure Variables

• Hints for Choosing Between IF and CASE Statements

• Loop in Stored Procedures

• MySQL Cursor

• Introduction to MySQL Stored Procedures

• Listing Stored Procedures in a MySQL Database

原文链接：http://outofmemory.cn/mysql/procedure/getting-started-with-mysql-stored-procedures