**一、触发器部分**
- 订单表中增加订单数量后，商品表商品数量同步减少对应的商品订单出数量
CREATE TRIGGER update_goods_num_after_insert_orders
AFTER INSERT ON orders
FOR EACH ROW
UPDATE goods
SET num = num - NEW.onum
WHERE gid = NEW.gid;
-- 测试
INSERT INTO orders (gid, name, price, onum, otime)
VALUES ('A0001', '橡皮', 2.5, 10, '2024-07-25');
- 客户取消订单，恢复商品表对应商品的数量
CREATE TRIGGER restore_goods_num_after_cancel_order
AFTER DELETE ON orders
FOR EACH ROW
UPDATE goods
SET num = num + OLD.onum
WHERE gid = OLD.gid;
-- 测试
DELETE FROM orders WHERE oid = 1;
- 客户修改订单，商品表对应商品数量同步更新
CREATE TRIGGER update_goods_num_after_update_orders
AFTER UPDATE ON orders
FOR EACH ROW
UPDATE goods
SET num = num + OLD.onum - NEW.onum
WHERE gid = NEW.gid;
-- 测试
UPDATE orders SET onum = 20 WHERE oid = 2;
**二、存储过程部分**
- 创建提取 `emp_new` 表所有员工姓名和工资的存储过程 `s1`
USE mydb7_openlab;
CREATE PROCEDURE s1()
SELECT name, salary FROM emp_new;
- 创建存储过程 `s2`，实现输入员工姓名后返回员工的年龄
CREATE PROCEDURE s2(IN emp_name VARCHAR(50))
SELECT age FROM emp_new WHERE name = emp_name;
- 创建一个存储过程 `s3`，有 2 个参数，传入部门号，返回该部门的平均工资
CREATE PROCEDURE s3(IN dept_id INT, OUT avg_salary DECIMAL(10, 2))
SELECT AVG(salary) INTO avg_salary FROM emp_new WHERE department_id = dept_id;
