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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