'message'

第十七章、练习题.sql

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+#第十七章、练习题
+
+USE dbtest17;
+
+#练习1
+#0、准备工作
+CREATE TABLE emps
+AS
+SELECT employee_id,last_name,salary
+FROM atguigudb.employees;
+
+SELECT * FROM emps;
+
+#1、复制一张emps表的空表emps_back，只有表结构，不包含任何数据
+CREATE TABLE emps_back
+AS
+SELECT * FROM emps
+WHERE FALSE;
+
+#老师讲的
+CREATE TABLE emps_back
+AS
+SELECT * FROM emps
+WHERE 1 = 2;
+
+#2、查询emps_back表中的数据
+SELECT * FROM emps_back;
+
+#3、创建触发器emps_insert_trigger，每当向emps表中添加一条记录时，同步将这条记录添加到emps_back表中
+DELIMITER //
+
+CREATE TRIGGER emps_insert_trigger
+AFTER INSERT ON emps
+FOR EACH ROW
+BEGIN
+		#将新添加到emps表中的记录添加到emps_back表中
+		INSERT INTO emps_back(employee_id,last_name,salary)
+		VALUES(NEW.employee_id,NEW.last_name,NEW.salary);
+END //
+
+DELIMITER ;
+
+SHOW TRIGGERS;
+
+#4、验证触发器是否起作用
+INSERT INTO emps(employee_id,last_name,salary)
+VALUES(300,'Tom',3400);
+
+SELECT * FROM emps;
+
+SELECT * FROM emps_back;
+
+
+#练习2
+#0、准备工作：使用练习1中的emps表
+
+#1、复制一张emps表的空表emps_back1，只有表结构，不包含任何数据
+CREATE TABLE emps_back1
+AS
+SELECT * FROM emps
+WHERE 1 = 2;
+
+#2、查询emps_back1表中的数据
+SELECT * FROM emps_back1;
+
+#3、创建触发器emps_del_trigger，每当向emps表中删除一条记录时，同步将删除的这条记录添加到emps_back1表中
+DELIMITER //
+
+CREATE TRIGGER emps_del_trigger
+BEFORE DELETE ON emps
+FOR EACH ROW
+BEGIN
+		#将emps表中删除的记录，添加到emps_back1表中
+		INSERT INTO emps_back1(employee_id,last_name,salary)
+		VALUES(OLD.employee_id,OLD.last_name,OLD.salary);
+END //
+
+DELIMITER ;
+
+#4、验证触发器是否起作用
+DELETE FROM emps
+WHERE employee_id = 101;
+
+SELECT * FROM emps;
+
+SELECT * FROM emps_back1;
+
+#补充，如果要把emps表的数据全部删除，并把数据全部添加到emps_back1表中，只需要将WHERE语句去掉就可以了。
+
+
+
+
+
+
+
+
+
+
+

第十七章、触发器.sql

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+#第十七章、触发器
+
+#0、准备工作
+CREATE DATABASE dbtest17;
+
+USE dbtest17;
+
+#1、如果创建触发器
+
+#举例1
+
+#①、创建数据表
+
+CREATE TABLE test_trigger (
+id INT PRIMARY KEY AUTO_INCREMENT,
+t_note VARCHAR(30)
+);
+
+CREATE TABLE test_trigger_log (
+id INT PRIMARY KEY AUTO_INCREMENT,
+t_log VARCHAR(30)
+);
+
+#②、查看表数据
+SELECT * FROM test_trigger;
+
+SELECT * FROM test_trigger_log;
+
+#③、创建触发器
+#创建触发器：创建名称为before_insert_test_tri的触发器，向test_trigger数据表插入
+#数据之前，向test_trigger_log数据表中插入before_insert的日志信息。
+
+DELIMITER //
+
+CREATE TRIGGER before_insert_test_tri
+BEFORE INSERT ON test_trigger
+FOR EACH ROW
+BEGIN
+			INSERT INTO test_trigger_log(t_log)
+			VALUES('before insert ...');
+END //
+
+DELIMITER ;
+
+#④、测试
+INSERT INTO test_trigger(t_note)
+VALUES('Tom ...');
+
+SELECT * FROM test_trigger;
+
+SELECT * FROM test_trigger_log;
+
+#举例2：
+#创建名称为after_insert_test_tri的触发器，向test_trigger数据表插入数据之后，
+#向test_trigger_log数据表中插入after_insert的日志信息。
+
+DELIMITER //
+
+CREATE TRIGGER after_insert_test_tri
+AFTER INSERT ON test_trigger
+FOR EACH ROW
+BEGIN
+		INSERT INTO test_trigger_log(t_log)
+		VALUES('affter insert ...');
+END //
+
+DELIMITER ;
+
+#测试
+INSERT INTO test_trigger(t_note)
+VALUES('Jerry ...');
+
+SELECT * FROM test_trigger;
+
+SELECT * FROM test_trigger_log;
+
+#举例3：
+#定义触发器“salary_check_trigger”，基于员工表“employees”的INSERT事件，
+#在INSERT之前检查将要添加的新员工薪资是否大于他领导的薪资，如果大于领导薪资，
+#则报sqlstate_value为'HY000'的错误，从而使得添加失败。
+
+#准备工作
+CREATE TABLE employees
+AS
+SELECT * FROM atguigudb.employees;
+
+CREATE TABLE departments
+AS
+SELECT * FROM atguigudb.departments;
+
+DESC employees;
+
+#创建触发器
+DELIMITER //
+
+CREATE TRIGGER salary_check_trigger
+BEFORE INSERT ON employees
+FOR EACH ROW
+BEGIN
+		#查询到要添加的数据的manager的薪资
+		DECLARE mgr_sal DOUBLE;
+		
+		SELECT salary INTO mgr_sal FROM employees
+		WHERE employee_id = NEW.manager_id;
+		
+		IF NEW.salary > mgr_sal
+			THEN SIGNAL SQLSTATE 'HY000' SET MESSAGE_TEXT = '薪资高于领导薪资错误';
+		END IF;
+END //
+
+DELIMITER ;
+
+#测试
+#添加成功：依然触发了触发器salary_check_trigger的执行
+
+INSERT INTO employees(employee_id,last_name,email,hire_date,job_id,salary,manager_id)
+VALUES(300,'Tom','tom@126.com',CURDATE(),'AD_VP',8000,103);
+
+#添加失败
+INSERT INTO employees(employee_id,last_name,email,hire_date,job_id,salary,manager_id)
+VALUES(300,'Tom1','tom@126.com',CURDATE(),'AD_VP',10000,103);
+
+SELECT * FROM employees;
+
+#2、查看触发器
+#①、查看当前数据库的左右触发器的定义
+
+SHOW TRIGGERS;
+
+#②、方式2：查看当前数据库中某个触发器的定义
+SHOW CREATE TRIGGER salary_check_trigger;
+
+#③、方式3：从系统库information_schema的TRIGGERS表中查询“salary_check_trigger”触发器的信息。
+SELECT * FROM information_schema.TRIGGERS;
+
+#3、删除触发器
+DROP TRIGGER IF EXISTS after_insert_test_tri;
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+

第十八章、MySQL8.0的其它新特性.sql

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+#第十八章、MySQL8.0的其它新特性
+
+CREATE DATABASE dbtest18;
+
+USE dbtest18;
+
+#一、窗口函数
+
+#1.1、演示窗口函数的效果
+CREATE TABLE sales(
+id INT PRIMARY KEY AUTO_INCREMENT,
+city VARCHAR(15),
+county VARCHAR(15),
+sales_value DECIMAL
+);
+
+INSERT INTO sales(city,county,sales_value)
+VALUES
+('北京','海淀',10.00),
+('北京','朝阳',20.00),
+('上海','黄埔',30.00),
+('上海','长宁',10.00);
+
+SELECT * FROM sales;
+
+#需求：现在计算这个网站在每个城市的销售总额、在全国的销售总额、每个区的销售额
+#占所在城市销售额中的比率，以及占总销售额中的比率。
+
+#方式一：
+CREATE TEMPORARY TABLE a       -- 创建临时表
+SELECT SUM(sales_value) AS sales_value -- 计算总计金额
+FROM sales;
+
+SELECT * FROM a;
+
+CREATE TEMPORARY TABLE b    -- 创建临时表
+SELECT city,SUM(sales_value) AS sales_value  -- 计算城市销售合计
+FROM sales
+GROUP BY city;
+
+SELECT * FROM b;
+
+SELECT s.city AS 城市,s.county AS 区,s.sales_value AS 区销售额,
+			b.sales_value AS 市销售额,s.sales_value/b.sales_value AS 市比率,
+			a.sales_value AS 总销售额,s.sales_value/a.sales_value AS 总比率
+FROM sales s
+JOIN b ON (s.city=b.city) -- 连接市统计结果临时表
+JOIN a                   -- 连接总计金额临时表
+ORDER BY s.city,s.county;
+
+#方式二：
+SELECT city AS 城市,county AS 区,sales_value AS 区销售额,
+SUM(sales_value) OVER(PARTITION BY city) AS 市销售额,  -- 计算市销售额
+sales_value/SUM(sales_value) OVER(PARTITION BY city) AS 市比率,
+SUM(sales_value) OVER() AS 总销售额,   -- 计算总销售额
+sales_value/SUM(sales_value) OVER() AS 总比率
+FROM sales
+ORDER BY city,county;
+
+#2、介绍窗口函数
+CREATE TABLE employees
+AS
+SELECT * FROM atguigudb.employees;
+
+SELECT * FROM employees;
+
+#准备工作
+CREATE TABLE goods(
+id INT PRIMARY KEY AUTO_INCREMENT,
+category_id INT,
+category VARCHAR(15),
+NAME VARCHAR(30),
+price DECIMAL(10,2),
+stock INT,
+upper_time DATETIME
+);
+
+INSERT INTO goods(category_id,category,NAME,price,stock,upper_time)
+VALUES
+(1, '女装/女士精品', 'T恤', 39.90, 1000, '2020-11-10 00:00:00'),
+(1, '女装/女士精品', '连衣裙', 79.90, 2500, '2020-11-10 00:00:00'),
+(2, '户外运动', '骑行装备', 399.90, 3500, '2020-11-10 00:00:00'),
+(1, '女装/女士精品', '牛仔裤', 89.90, 3500, '2020-11-10 00:00:00'),
+(2, '户外运动', '山地自行车', 1399.90, 2500, '2020-11-10 00:00:00'),
+(1, '女装/女士精品', '呢绒外套', 399.90, 1200, '2020-11-10 00:00:00'),
+(2, '户外运动', '自行车', 399.90, 1000, '2020-11-10 00:00:00'),
+(2, '户外运动', '登山杖', 59.90, 1500, '2020-11-10 00:00:00'),
+(1, '女装/女士精品', '卫衣', 89.90, 1500, '2020-11-10 00:00:00'),
+(2, '户外运动', '运动外套', 799.90, 500, '2020-11-10 00:00:00'),
+(1, '女装/女士精品', '百褶裙', 29.90, 500, '2020-11-10 00:00:00'),
+(2, '户外运动', '滑板', 499.90, 1200, '2020-11-10 00:00:00');
+
+SELECT * FROM goods;
+
+#1、序号函数
+#1.1、ROW_NUMBER()函数
+#举例1：查询 goods 数据表中每个商品分类下价格降序排列的各个商品信息。
+SELECT ROW_NUMBER() OVER(PARTITION BY category_id ORDER BY price DESC) AS row_num,
+id, category_id, category, NAME, price, stock
+FROM goods;
+
+#举例2：查询 goods 数据表中每个商品分类下价格最高的3种商品信息。
+SELECT *
+FROM (SELECT ROW_NUMBER() OVER(PARTITION BY category_id ORDER BY price DESC) 		AS row_num,
+		id, category_id, category, NAME, price, stock
+		FROM goods) t
+WHERE row_num <= 3;
+
+#1.2、RANK()函数
+#举例1：使用RANK()函数获取 goods 数据表中各类别的价格从高到低排序的各商品信息。
+SELECT RANK() OVER(PARTITION BY category_id ORDER BY price DESC) AS row_num,
+id, category_id, category, NAME, price, stock
+FROM goods;
+
+#举例2：使用RANK()函数获取 goods 数据表中类别为“女装/女士精品”的价格最高的4款商品信息。
+
+SELECT *
+FROM(
+	SELECT RANK() OVER(PARTITION BY category_id ORDER BY price DESC) AS row_num,
+	id, category_id, category, NAME, price, stock
+	FROM goods) t
+WHERE category_id = 1 AND row_num <= 4;
+
+#1.3、DENSE_RANK()函数
+#举例1：使用DENSE_RANK()函数获取 goods 数据表中各类别的价格从高到低排序的各商品信息。
+
+SELECT DENSE_RANK() OVER(PARTITION BY category_id ORDER BY price DESC) AS row_num,
+id, category_id, category, NAME, price, stock
+FROM goods;
+
+#举例2：使用DENSE_RANK()函数获取 goods 数据表中类别为“女装/女士精品”的价格最高的4款商品信息。
+
+SELECT *
+FROM(
+	SELECT DENSE_RANK() OVER(PARTITION BY category_id ORDER BY price DESC) AS 	row_num,
+	id, category_id, category, NAME, price, stock
+	FROM goods) t
+WHERE category_id = 1 AND row_num <= 3;
+
+#2、分布函数
+
+#2.1、PERCENT_RANK()函数
+#举例：计算 goods 数据表中名称为“女装/女士精品”的类别下的商品的PERCENT_RANK值。
+#写法一：
+SELECT RANK() OVER w AS r,
+PERCENT_RANK() OVER w AS pr,
+id, category_id, category, NAME, price, stock
+FROM goods
+WHERE category_id = 1 WINDOW w AS (PARTITION BY category_id ORDER BY price DESC);
+
+#写法二：
+SELECT RANK() OVER (PARTITION BY category_id ORDER BY price DESC) AS r,
+PERCENT_RANK() OVER (PARTITION BY category_id ORDER BY price DESC) AS pr,
+id, category_id, category, NAME, price, stock
+FROM goods
+WHERE category_id = 1;
+
+#2.2、CUME_DIST()函数
+#举例：查询goods数据表中小于或等于当前价格的比例。
+SELECT CUME_DIST() OVER(PARTITION BY category_id ORDER BY price ASC) AS cd,
+id, category, NAME, price
+FROM goods;
+
+#3、前后函数
+#3.1、LAG(expr,n)函数
+#举例：查询goods数据表中前一个商品价格与当前商品价格的差值。
+
+SELECT id, category, NAME, price, pre_price, price - pre_price AS diff_price
+FROM (
+	SELECT  id, category, NAME, price,LAG(price,1) OVER w AS pre_price
+	FROM goods
+	WINDOW w AS (PARTITION BY category_id ORDER BY price)) t;
+	
+#其中，子查询如下：
+SELECT  id, category, NAME, price,LAG(price,1) OVER (PARTITION BY category_id ORDER BY price) AS pre_price
+FROM goods;
+
+#3.2、LEAD(expr,n)函数
+#举例：查询goods数据表中后一个商品价格与当前商品价格的差值。
+SELECT id, category, NAME, behind_price, price,behind_price - price AS diff_price
+FROM(
+	SELECT id, category, NAME, price,LEAD(price, 1) OVER w AS behind_price
+	FROM goods WINDOW w AS (PARTITION BY category_id ORDER BY price)) t;
+
+#其中，子查询为：
+SELECT id, category, NAME, price,LEAD(price, 1) OVER (PARTITION BY category_id ORDER BY price) AS behind_price
+FROM goods;
+
+#4、首尾函数
+#4.1、FIRST_VALUE(expr)函数
+#举例：按照价格排序，查询第1个商品的价格信息。
+
+SELECT id, category, NAME, price, stock,FIRST_VALUE(price) OVER w AS first_price
+FROM goods WINDOW w AS (PARTITION BY category_id ORDER BY price);
+
+#4.2、LAST_VALUE(expr)函数
+SELECT id, category, NAME, price, stock,LAST_VALUE(price) OVER w AS last_price
+FROM goods WINDOW w AS (PARTITION BY category_id ORDER BY price);
+
+#5、其他函数
+#5.1、NTH_VALUE(expr,n)函数
+#举例：查询goods数据表中排名第2和第3的价格信息。
+
+SELECT id, category,NAME,price,
+	NTH_VALUE(price,2) OVER w AS second_price,
+	NTH_VALUE(price,3) OVER w AS third_price
+FROM goods WINDOW w AS (PARTITION BY category_id ORDER BY price);
+
+#5.2、NTILE(n)函数
+#举例：将goods表中的商品按照价格分为3组。
+
+SELECT NTILE(3) OVER w AS nt,id, category, NAME, price
+FROM goods WINDOW w AS (PARTITION BY category_id ORDER BY price);
+
+#二、新特性2：公用表表达式
+
+#2.1、普通公用表表达式
+#举例：查询员工所在的部门的详细信息。
+#准备工作
+CREATE TABLE departments
+AS
+SELECT * FROM atguigudb.departments;
+
+#子查询实现
+SELECT * FROM departments
+WHERE department_id IN (
+												SELECT DISTINCT department_id
+												FROM employees
+												);
+
+#CTE实现
+WITH cte_emp
+AS (SELECT DISTINCT department_id FROM employees)
+
+SELECT * 
+FROM departments d JOIN cte_emp e
+ON d.department_id = e.department_id;
+
+#2.2、递归公用表表达式
+#举例：找出公司employees表中所有的下下属。
+WITH RECURSIVE cte 
+AS 
+(
+SELECT employee_id,last_name,manager_id,1 AS n FROM employees WHERE employee_id = 100 -- 种子查询，找到第一代领导
+UNION ALL
+SELECT a.employee_id,a.last_name,a.manager_id,n+1 FROM employees AS a JOIN cte
+ON (a.manager_id = cte.employee_id) -- 递归查询，找出以递归公用表表达式的人为领导的人
+)
+SELECT employee_id,last_name FROM cte WHERE n >= 3; 
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+

第十八章、练习题.sql

@@ -0,0 +1,45 @@
+#第十八章、练习题
+
+USE dbtest18;
+
+#1、创建students数据表，如下：
+CREATE TABLE students(
+id INT PRIMARY KEY AUTO_INCREMENT,
+student VARCHAR(15),
+points TINYINT
+);
+
+#2. 向表中添加数据如下
+INSERT INTO students(student,points)
+VALUES
+('张三',89),
+('李四',77),
+('王五',88),
+('赵六',90),
+('孙七',90),
+('周八',88);
+
+#3. 分别使用RANK()、DENSE_RANK() 和 ROW_NUMBER()函数对学生成绩降序排列情况进行显示
+
+#方式一：
+SELECT
+ROW_NUMBER() OVER (ORDER BY points DESC) AS "排序1",
+RANK() OVER (ORDER BY points DESC) AS "排序2",
+DENSE_RANK() OVER (ORDER BY points DESC) AS "排序3",
+student,points
+FROM students;
+
+#方式二
+SELECT
+ROW_NUMBER() OVER w AS "排序1",
+RANK() OVER w AS "排序2",
+DENSE_RANK() OVER w AS "排序3",
+student,points
+FROM students WINDOW w AS (ORDER BY points DESC);
+
+
+
+
+
+
+