MySQL存储过程
DELIMITER $$
DROP PROCEDURE IF EXISTS HelloWorld$$
CREATE PROCEDURE HelloWorld()
BEGIN
SELECT "Hello World!";
END$$
DELIMITER ;
3，变量
DECLARE声明，SET赋值
可以在DECLARE变量时用DEFAULT设置默认值，不设则为NULL
DECLARE counter INT DEFAULT 0;
SET counter = counter+1;4，参数
IN为默认类型，值必须在调用时指定，值不能返回（值传递）
OUT值可以返回（指针传递）
INOUT值必须在调用时指定，值可以返回
CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)
CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)
5，条件判断
IF THEN、ELSEIF、ELSE、END IF
代码
DELIMITER $$
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$$
DELIMITER ;
6，循环
LOOP、END LOOP
代码
CREATE PROCEDURE simple_loop(OUT counter INT)
BEGIN
SET counter = 0;
my_simple_loop: LOOP
SET counter = counter+1;
IF counter = 10 THEN
LEAVE my_simple_loop;
END IF;
END LOOP my_simple_loop;
END$$
WHILE DO、END WHILE
代码
CREATE PROCEDURE simple_while(OUT counter INT)
BEGIN
SET counter = 0;
WHILE counter != 10 DO
SET counter = counter+1;
END WHILE;
END$$
DELIMITER ;
REPEAT、UNTILL
代码
CREATE PROCEDURE simple_repeat(OUT counter INT)
BEGIN
SET counter = 0;
REPEAT
SET counter = counter+1;
UNTIL counter = 10 END REPEAT;
END$$
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
代码
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$$
DELIMITER ; unbounded SELECT语句用于存储过程返回结果集
代码
CREATE PROCEDURE sp_emps_in_dept(in_employee_id INT)
BEGIN
SELECT employee_id, surname, firstname, address1, address2, zipcode, date_of_birth FROM employees WHERE department_id=in_employee_id;
END$$
DELIMITER ; UPDATE、INSERT、DELETE、CREATE TABLE等非查询语句也可以嵌入存储过程里
代码
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$$
DELIMITER ;
9，使用CALL调用存储程序
代码
CREATE PROCEDURE call_example(employee_id INT, employee_type VARCHAR(20))
NO SQL
BEGIN
DECLARE l_bonus_amount NUMERIC(8,2);
IF employee_type='MANAGER' THEN
CALL calc_manager_bonus(employee_id, l_bonus_amount);
ELSE
CALL calc_minion_bonus(employee_id, l_bonus_amount);
END IF;
CALL grant_bonus(employee_id, l_bonus_amount);
END$$
DELIMITER ;
10，一个复杂的例子
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;
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：
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 各参数说明见CREATE PROCEDURE and CREATE FUNCTION Syntax
例子：
代码
DELIMITER
DROPFUNCTIONIFEXISTSfdiscountprice
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$$
DELIMITER ;
12，触发器
触发器在INSERT、UPDATE或DELETE等DML语句修改数据库表时触发
触发器的典型应用场景是重要的业务逻辑、提高性能、监控表的修改等
触发器可以在DML语句执行前或后触发
代码
CREATE TRIGGER sales_trigger
BEFORE INSERT ON sales
FOR EACH ROW
BEGIN
IF NEW.sale_value > 500 THEN
SET NEW.free_shipping = 'Y';
ELSE
SET NEW.free_shipping = 'N';
END IF;
IF NEW.sale_value > 1000 THEN
SET NEW.discount = NEW.sale_value * .15;
ELSE
SET NEW.discount = 0;
END IF;
END$$
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