MySQL 存储过程经常使用语法

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MySQL 存储过程经常使用语法
MySQL 存储过程是从 MySQL 5.0 開始添加的新功能。存储过程的长处有一箩筐。只是最基本的还是运行效率和SQL 代码封装。特别是 SQL 代码封装功能，假设没有存储过程，在外部程序訪问数据库时（比如 PHP），要组织非常多 SQL 语句。特别是业务逻辑复杂的时候，一大堆的 SQL 和条件夹杂在 PHP 代码中，让人不寒而栗。如今有了 MySQL 存储过程，业务逻辑能够封装存储过程中，这样不仅easy维护，并且运行效率也高。

一、MySQL 创建存储过程
“pr_add” 是个简单的 MySQL 存储过程，这个存储过程有两个 int 类型的输入參数 “a”、“b”，返回这两个參数的和。

drop procedure if exists pr_add;

-- 计算两个数之和

create procedure pr_add
(
   a int,
   b int
)
begin
   declare c int;

   if a is null then
      set a = 0;
   end if;

   if b is null then
      set b = 0;
   end if;

   set c = a + b;

   select c as sum;

   /*
   return c;- 不能在 MySQL 存储过程中使用。return 仅仅能出如今函数中。
/
end;
二、调用 MySQL 存储过程
call pr_add(10, 20);
运行 MySQL 存储过程，存储过程參数为 MySQL 用户变量。

set @a = 10;
set @b = 20;

call pr_add(@a, @b);
三、MySQL 存储过程特点
创建 MySQL 存储过程的简单语法为：

create procedure 存储过程名字()
(
   [in|out|inout] 參数 datatype
)
begin
   MySQL 语句;
end;
MySQL 存储过程參数假设不显式指定“in”、“out”、“inout”，则默觉得“in”。习惯上，对于是“in” 的參数，我们都不会显式指定。

1. MySQL 存储过程名字后面的“()”是必须的，即使没有一个參数，也须要“()”

2. MySQL 存储过程參数，不能在參数名称前加“@”，如：“@a int”。以下的创建存储过程语法在 MySQL 中是错误的（在 SQL Server 中是正确的）。 MySQL 存储过程中的变量，不须要在变量名字前加“@”，尽管 MySQL client用户变量要加个“@”。

create procedure pr_add
(
   @a int,- 错误
   b int   - 正确
)
3. MySQL 存储过程的參数不能指定默认值。

4. MySQL 存储过程不须要在 procedure body 前面加 “as”。而 SQL Server 存储过程必须加 “as” keyword。

create procedure pr_add
(
   a int,
   b int
)
as             - 错误，MySQL 不须要 “as”
begin
   mysql statement ...;
end;
5. 假设 MySQL 存储过程中包括多条 MySQL 语句，则须要 begin end keyword。

create procedure pr_add
(
   a int,
   b int
)
begin
   mysql statement 1 ...;
   mysql statement 2 ...;
end;
6. MySQL 存储过程中的每条语句的末尾，都要加上分号 “;”

   ...

   declare c int;

   if a is null then
      set a = 0;
   end if;

   ...
end;
7. MySQL 存储过程中的凝视。

   /*
     这是个
     多行 MySQL 凝视。
/

   declare c int;    - 这是单行 MySQL 凝视（注意- 后至少要有一个空格）

   if a is null then 这也是个单行 MySQL 凝视
      set a = 0;
   end if;

   ...
end;
8. 不能在 MySQL 存储过程中使用 “return” keyword。

   set c = a + b;

   select c as sum;

   /*
   return c;- 不能在 MySQL 存储过程中使用。return 仅仅能出如今函数中。
/
end;
9. 调用 MySQL 存储过程时候，须要在过程名字后面加“()”，即使没有一个參数，也须要“()”

call pr_no_param();
10. 由于 MySQL 存储过程參数没有默认值，所以在调用 MySQL 存储过程时候，不能省略參数。能够用 null 来替代。

call pr_add(10, null);

1，前提
须要MySQL 5

2，Hello World
MySQL存储过程之Hello World

Java代码

DELIMITER $$



DROP PROCEDURE IF EXISTS HelloWorld$$

CREATE PROCEDURE HelloWorld()

BEGIN

    SELECT "Hello World!";

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS HelloWorld$$ CREATE PROCEDURE HelloWorld() BEGIN SELECT "Hello World!"; END$$ DELIMITER ;

3，变量
使用DECLARE来声明，DEFAULT赋默认值，SET赋值

Java代码

DECLARE counter INT DEFAULT 0;

SET counter = counter+1;

DECLARE counter INT DEFAULT 0; SET counter = counter+1;

4，參数
IN为默认类型，值必须在调用时指定，值不能返回（值传递）
OUT值能够返回（指针传递）
INOUT值必须在调用时指定，值能够返回

Java代码

CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)

CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)

5，条件推断
IF THEN、ELSEIF、ELSE、END IF

Java代码

DELIMITER $$



DROP PROCEDURE IF EXISTS discounted_price$$

CREATE PROCEDURE discunted_price(normal_price NUMERIC(8, 2), OUT discount_price NUMERIC(8, 2))

BEGIN

    IF (normal_price > 500) THEN

        SET discount_price = normal_price * .8;

    ELSEIF (normal_price > 100) THEN

        SET discount_price = normal_price * .9;

    ELSE

        SET discount_price = normal_price;

    END IF;

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS discounted_price$$ CREATE PROCEDURE discunted_price(normal_price NUMERIC(8, 2), OUT discount_price NUMERIC(8, 2)) BEGIN IF (normal_price > 500) THEN SET discount_price = normal_price * .8; ELSEIF (normal_price > 100) THEN SET discount_price = normal_price * .9; ELSE SET discount_price = normal_price; END IF; END$$ DELIMITER ;

6，循环
LOOP、END LOOP

Java代码

DELIMITER $$



DROP PROCEDURE IF EXISTS simple_loop$$



CREATE PROCEDURE simple_loop(OUT counter INT)

BEGIN

    SET counter = 0;

    my_simple_loop: LOOP

        SET counter = counter+1;

        IF counter = 10 THEN

            LEAVE my_simple_loop;

        END IF;

    END LOOP my_simple_loop;

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS simple_loop$$ CREATE PROCEDURE simple_loop(OUT counter INT) BEGIN SET counter = 0; my_simple_loop: LOOP SET counter = counter+1; IF counter = 10 THEN LEAVE my_simple_loop; END IF; END LOOP my_simple_loop; END$$ DELIMITER ;

WHILE DO、END WHILE

Java代码

DELIMITER $$



DROP PROCEDURE IF EXISTS simple_while$$



CREATE PROCEDURE simple_while(OUT counter INT)

BEGIN

    SET counter = 0;

    WHILE counter != 10 DO

        SET counter = counter+1;

    END WHILE;

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS simple_while$$ CREATE PROCEDURE simple_while(OUT counter INT) BEGIN SET counter = 0; WHILE counter != 10 DO SET counter = counter+1; END WHILE; END$$ DELIMITER ;

REPEAT、UNTILL

Java代码

DELIMITER $$



DROP PROCEDURE IF EXISTS simple_repeat$$



CREATE PROCEDURE simple_repeat(OUT counter INT)

BEGIN

    SET counter = 0;

    REPEAT

        SET counter = counter+1;

    UNTIL counter = 10 END REPEAT;

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS simple_repeat$$ CREATE PROCEDURE simple_repeat(OUT counter INT) BEGIN SET counter = 0; REPEAT SET counter = counter+1; UNTIL counter = 10 END REPEAT; END$$ DELIMITER ;

7，异常处理
假设用cursor获取SELECT语句返回的全部结果集时应该定义NOT FOUND error handler来防止存储程序提前终结
假设SQL语句可能返回constraint violation等错误时应该创建一个handler来防止程序终结

8，数据库交互
INTO用于存储单行记录的查询结果

Java代码

DECLARE total_sales NUMERIC(8, 2);

SELECT SUM(sale_value) INTO total_sales FROM sales WHERE customer_id=in_customer_id;

DECLARE total_sales NUMERIC(8, 2); SELECT SUM(sale_value) INTO total_sales FROM sales WHERE customer_id=in_customer_id;

CURSOR用于处理多行记录的查询结果

Java代码

DELIMITER $$



DROP PROCEDURE IF EXITS cursor_example$$

CREATE PROCEDURE cursor_example()

    READS SQL DATA

BEGIN

    DECLARE l_employee_id INT;

    DECLARE l_salary NUMERIC(8,2);

    DECLARE l_department_id INT;

    DECLARE done INT DEFAULT 0;

    DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;



    OPEN cur1;

    emp_loop: LOOP

        FETCH cur1 INTO l_employee_id, l_salary, l_department_id;

        IF done=1 THEN

            LEAVE emp_loop;

        END IF;

    END LOOP emp_loop;

    CLOSE cur1;

END$$

DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXITS cursor_example$$ CREATE PROCEDURE cursor_example() READS SQL DATA BEGIN DECLARE l_employee_id INT; DECLARE l_salary NUMERIC(8,2); DECLARE l_department_id INT; DECLARE done INT DEFAULT 0; DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1; OPEN cur1; emp_loop: LOOP FETCH cur1 INTO l_employee_id, l_salary, l_department_id; IF done=1 THEN LEAVE emp_loop; END IF; END LOOP emp_loop; CLOSE cur1; END$$ DELIMITER ;

unbounded SELECT语句用于存储过程返回结果集

Java代码

DELIMITER $$

DROP PROCEDURE IF EXISTS sp_emps_in_dept$$

CREATE PROCEDURE sp_emps_in_dept(in_employee_id INT)

BEGIN

    SELECT employee_id, surname, firstname, address1, address2, zipcode, date_of_birth FROM employees WHERE department_id=in_employee_id;

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS sp_emps_in_dept$$ CREATE PROCEDURE sp_emps_in_dept(in_employee_id INT) BEGIN SELECT employee_id, surname, firstname, address1, address2, zipcode, date_of_birth FROM employees WHERE department_id=in_employee_id; END$$ DELIMITER ;

UPDATE、INSERT、DELETE、CREATE TABLE等非查询语句也能够嵌入存储过程里

Java代码

DELIMITER $$



DROP PROCEDURE IF EXITS sp_update_salary$$

CREATE PROCEDURE sp_update_salary(in_employee_id INT, in_new_salary NUMERIC(8,2))

BEGIN

    IF in_new_salary < 5000 OR in_new_salary > 500000 THEN

        SELECT "Illegal salary: salary must be between $5000 and $500, 000";

    ELSE

        UPDATE employees SET salary=in_new_salary WHERE employee_id=in_employee_id;

    END IF:

END$$



DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXITS sp_update_salary$$ CREATE PROCEDURE sp_update_salary(in_employee_id INT, in_new_salary NUMERIC(8,2)) BEGIN IF in_new_salary < 5000 OR in_new_salary > 500000 THEN SELECT "Illegal salary: salary must be between $5000 and $500, 000"; ELSE UPDATE employees SET salary=in_new_salary WHERE employee_id=in_employee_id; END IF: END$$ DELIMITER ;

9，使用CALL调用存储程序

Java代码

DELIMITER $$



DROP PROCEDURE IF EXISTS call_example$$

CREATE PROCEDURE call_example(employee_id INT, employee_type VARCHAR(20))

    NO SQL

BEGIN

    DECLARE l_bonus_amount NUMERIC(8,2);



    IF employee_type='MANAGER' THEN

        CALL calc_manager_bonus(employee_id, l_bonus_amount);

    ELSE

        CALL calc_minion_bonus(employee_id, l_bonus_amount);

    END IF;

    CALL grant_bonus(employee_id, l_bonus_amount);

END$$

DELIMITER ;

DELIMITER $$ DROP PROCEDURE IF EXISTS call_example$$ CREATE PROCEDURE call_example(employee_id INT, employee_type VARCHAR(20)) NO SQL BEGIN DECLARE l_bonus_amount NUMERIC(8,2); IF employee_type='MANAGER' THEN CALL calc_manager_bonus(employee_id, l_bonus_amount); ELSE CALL calc_minion_bonus(employee_id, l_bonus_amount); END IF; CALL grant_bonus(employee_id, l_bonus_amount); END$$ DELIMITER ;

10，一个复杂的样例

Java代码

CREATE PROCEDURE putting_it_all_together(in_department_id INT)

    MODIFIES SQL DATA

BEGIN

    DECLARE l_employee_id INT;

    DECLARE l_salary NUMERIC(8,2);

    DECLARE l_department_id INT;

    DECLARE l_new_salary NUMERIC(8,2);

    DECLARE done INT DEFAULT 0;



    DECLARE cur1 CURSOR FOR

        SELECT employee_id, salary, department_id

        FROM employees

        WHERE department_id=in_department_id;



    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;



    CREATE TEMPORARY TABLE IF NOT EXISTS emp_raises

        (employee_id INT, department_id INT, new_salary NUMERIC(8,2));



    OPEN cur1;

    emp_loop: LOOP

        FETCH cur1 INTO l_employee_id, l_salary, l_department_id;

        IF done=1 THEN    /* No more rows */

            LEAVE emp_loop;

        END IF;

        CALL new_salary(1_employee_id, l_new_salary); /* Get new salary */

        IF (l_new_salary <> l_salary) THEN  /* Salary changed */

            UPDATE employees

                SET salary=l_new_salary

            WHERE employee_id=l_employee_id;

            /* Keep track of changed salaries */

            INSERT INTO emp_raises(employee_id, department_id, new_salary)

                VALUES (l_employee_id, l_department_id, l_new_salary);

        END IF:

    END LOOP emp_loop;

    CLOSE cur1;

    /* Print out the changed salaries */

    SELECT employee_id, department_id, new_salary from emp_raises

        ORDER BY employee_id;

END;

CREATE PROCEDURE putting_it_all_together(in_department_id INT) MODIFIES SQL DATA BEGIN DECLARE l_employee_id INT; DECLARE l_salary NUMERIC(8,2); DECLARE l_department_id INT; DECLARE l_new_salary NUMERIC(8,2); DECLARE done INT DEFAULT 0; DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees WHERE department_id=in_department_id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1; CREATE TEMPORARY TABLE IF NOT EXISTS emp_raises (employee_id INT, department_id INT, new_salary NUMERIC(8,2)); OPEN cur1; emp_loop: LOOP FETCH cur1 INTO l_employee_id, l_salary, l_department_id; IF done=1 THEN /* No more rows */ LEAVE emp_loop; END IF; CALL new_salary(1_employee_id, l_new_salary); /* Get new salary */ IF (l_new_salary <> l_salary) THEN /* Salary changed */ UPDATE employees SET salary=l_new_salary WHERE employee_id=l_employee_id; /* Keep track of changed salaries */ INSERT INTO emp_raises(employee_id, department_id, new_salary) VALUES (l_employee_id, l_department_id, l_new_salary); END IF: END LOOP emp_loop; CLOSE cur1; /* Print out the changed salaries */ SELECT employee_id, department_id, new_salary from emp_raises ORDER BY employee_id; END;

11，存储方法
存储方法与存储过程的差别
1，存储方法的參数列表仅仅同意IN类型的參数，并且不是必需也不同意指定INkeyword
2，存储方法返回一个单一的值，值的类型在存储方法的头部定义
3，存储方法能够在SQL语句内部调用
4，存储方法不能返回结果集
语法：

Java代码

CREATE

    [DEFINER = { user | CURRENT_USER }]

    PROCEDURE sp_name ([proc_parameter[,...]])

    [characteristic ...] routine_body



CREATE

    [DEFINER = { user | CURRENT_USER }]

    FUNCTION sp_name ([func_parameter[,...]])

    RETURNS type

    [characteristic ...] routine_body



proc_parameter:

    [ IN | OUT | INOUT ] param_name type



func_parameter:

    param_name type



type:

    Any valid MySQL data type



characteristic:

    LANGUAGE SQL

  | [NOT] DETERMINISTIC

  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }

  | SQL SECURITY { DEFINER | INVOKER }

  | COMMENT 'string'



routine_body:

    Valid SQL procedure statement

CREATE [DEFINER = { user | CURRENT_USER }] PROCEDURE sp_name ([proc_parameter[,...]]) [characteristic ...] routine_body CREATE [DEFINER = { user | CURRENT_USER }] FUNCTION sp_name ([func_parameter[,...]]) RETURNS type [characteristic ...] routine_body proc_parameter: [ IN | OUT | INOUT ] param_name type func_parameter: param_name type type: Any valid MySQL data type characteristic: LANGUAGE SQL | [NOT] DETERMINISTIC | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string' routine_body: Valid SQL procedure statement

各參数说明见CREATE PROCEDURE and CREATE FUNCTION Syntax
样例：

Java代码

DELIMITER $$



DROP FUNCTION IF EXISTS f_discount_price$$

CREATE FUNCTION f_discount_price

    (normal_price NUMERIC(8,2))

    RETURNS NUMERIC(8,2)

    DETERMINISTIC

BEGIN

    DECLARE discount_price NUMERIC(8,2);



    IF (normal_price > 500) THEN

        SET discount_price = normal_price * .8;

    ELSEIF (normal_price >100) THEN

        SET discount_price = normal_price * .9;

    ELSE

        SET discount_price = normal_price;

    END IF;



    RETURN(discount_price);

END$$



DELIMITER ;

DELIMITER $$ DROP FUNCTION IF EXISTS f_discount_price$$ CREATE FUNCTION f_discount_price (normal_price NUMERIC(8,2)) RETURNS NUMERIC(8,2) DETERMINISTIC BEGIN DECLARE discount_price NUMERIC(8,2); IF (normal_price > 500) THEN SET discount_price = normal_price * .8; ELSEIF (normal_price >100) THEN SET discount_price = normal_price * .9; ELSE SET discount_price = normal_price; END IF; RETURN(discount_price); END$$ DELIMITER ;

12，触发器
触发器在INSERT、UPDATE或DELETE等DML语句改动数据库表时触发
触发器的典型应用场景是重要的业务逻辑、提高性能、监控表的改动等
触发器能够在DML语句运行前或后触发

Java代码

DELIMITER $$



DROP TRIGGER sales_trigger$$

CREATE TRIGGER sales_trigger

    BEFORE INSERT ON sales

    FOR EACH ROW

BEGIN

    IF NEW.sale_value > 500 THEN

        SET NEW.free_shipping = 'Y';

    ELSE

        SET NEW.free_shipping = 'N';

    END IF;



    IF NEW.sale_value > 1000 THEN

        SET NEW.discount = NEW.sale_value * .15;

    ELSE

        SET NEW.discount = 0;

    END IF;

END$$



DELIMITER ;

转自：http://fyb613.blog.163.com/blog/static/325460922010044417672/
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原文地址：https://www.cnblogs.com/mfrbuaa/p/4314361.html

MySQL 存储过程 经常使用语法

MySQL 存储过程经常使用语法