mysql存储过程 基本语法
话不多说一、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 类型的输入参数 “a”、“b”，返回这两个参数的和。
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 只能出现在函数中。
/
end;
二、调用Mysql存储过程
eg： call pr_add(10,20);
执行 MySQL 存储过程，存储过程参数为 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()
(
参数 datatype
)
begin
MySQL 语句;
end;
MySQL 存储过程参数如果不显式指定“in”、“out”、“inout”，则默认为“in”。习惯上，对于是“in” 的参数，我们都不会显式指定。
如下，给出解释
1. MySQL 存储过程名字后面的“()”是必须的，即使没有一个参数，也需要“()”
2. MySQL 存储过程参数，不能在参数名称前加“@”，如：“@a int”。下面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，不需要在变量名字前加“@”，虽然 MySQL 客户端用户变量要加个“@”。
create procedure pr_add
(
@a int,- 错误
b int - 正确
)
3. MySQL 存储过程的参数不能指定默认值。
4. MySQL 存储过程不需要在 procedure body 前面加 “as”。而 SQL Server 存储过程必须加 “as” 关键字。
create procedure pr_add
(
a int,
b int
)
as - 错误，MySQL 不需要 “as”
begin
mysql statement ...;
end;
5. 如果 MySQL 存储过程中包含单条或者多条 MySQL 语句，都需要 begin end 关键字。
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;
...
7. MySQL 存储过程中的注释。
/*
这是个
多行 MySQL 注释。
/
declare c int; - 这是单行 MySQL 注释 （注意- 后至少要有一个空格）
if a is null then 这也是个单行 MySQL 注释
set a = 0;
end if;
...
end;
8. 不能在 MySQL 存储过程中使用 “return” 关键字。
set c = a + b;
select c as sum;
/*
return c;- 不能在 MySQL 存储过程中使用。return 只能出现在函数中。
/
end;
9. 调用 MySQL 存储过程时候，需要在过程名字后面加“()”，即使没有一个参数，也需要“()”
call pr_no_param();
10. 因为 MySQL 存储过程参数没有默认值，所以在调用 MySQL 存储过程时候，不能省略参数。可以用 null 来替代。
call pr_add(10, null);
1、当然以上这些，前提是 mysql 5
2、下面写一个mysql存储过程之 HelloWorld
[*] DELIMITER $$
[*]
[*] DROP PROCEDURE IF EXISTS HelloWorld$$
[*] CREATE PROCEDURE HelloWorld()
[*] BEGIN
[*] SELECT "Hello World!";
[*] END$$
[*]
[*] DELIMITER ;
3、变量
使用DECLARE来声明，DEFAULT赋默认值，SET赋值
[*] DECLARE counter INT DEFAULT 0;- 默认为0
[*] SET counter = counter+1; - 自增+1
4、参数
IN为默认类型，值必须在调用时指定，值不能返回（值传递）
OUT值可以返回（指针传递）
INOUT值必须在调用时指定，值可以返回
eg:
[*] CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)
5、条件判断
eg:
[*] DELIMITER $$
[*]
[*] 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
eg:
[*] 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$$
[*]
[*] DELIMITER ;
WHILE DO、END WHILE
[*] DELIMITER $$
[*]
[*] 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
[*] 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$$
[*]
[*] DELIMITER ;
7，异常处理
如果用cursor获取SELECT语句返回的所有结果集时应该定义NOT FOUND error handler来防止存储程序提前终结
如果SQL语句可能返回constraint violation等错误时应该创建一个handler来防止程序终结
8，数据库交互
INTO用于存储单行记录的查询结果
[*] DECLARE total_sales NUMERIC(8, 2);
[*] SELECT SUM(sale_value) INTO total_sales FROM sales WHERE customer_id=in_customer_id;
CURSOR用于处理多行记录的查询结果
[*] DELIMITER $$
[*]
[*] 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
[*] 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$$
[*]
[*] DELIMITER ;
UPDATE、INSERT、DELETE、CREATE TABLE等非查询语句也可以嵌入存储过程里
[*] DELIMITER $$
[*]
[*] 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
[*] 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 ;
10，一个复杂的例子
[*] 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_salaryl_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区别
1，存储方法的参数列表只允许IN类型的参数，而且没必要也不允许指定IN关键字
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，存储方法可以在SQL语句内部调用
4，存储方法不能返回结果集
语法：
[*] CREATE
[*]
[*] PROCEDURE sp_name (])
[*] routine_body
[*]
[*] CREATE
[*]
[*] FUNCTION sp_name (])
[*] RETURNS type
[*] routine_body
[*]
[*] proc_parameter:
[*] [ IN | OUT | INOUT ] param_name type
[*]
[*] func_parameter:
[*] param_name type
[*]
[*] type:
[*] Any valid MySQL data type
[*]
[*] characteristic:
[*] LANGUAGE SQL
[*] | DETERMINISTIC
[*] | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
[*] | SQL SECURITY { DEFINER | INVOKER }
[*] | COMMENT 'string'
[*]
[*] routine_body:
[*] Valid SQL procedure statement
各参数说明见CREATE PROCEDURE and CREATE FUNCTION Syntax
例子：
[*] 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语句修改数据库表时触发
触发器的典型应用场景是重要的业务逻辑、提高性能、监控表的修改等
触发器可以在DML语句执行前或后触发
[*]
[*] 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 ;
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