1、数据导入导出

• MySQL表导出,且是CSV格式
  我使用navicat导入导出，导出过程为：
  右键表名->导出向导->选择csv文件->下一步选择源表名->下一步选择导出字段->勾选包含列标题等配置->
  开始->导出成功
  

• 再将CSV表导入数据库
  右键表名->导入向导->选择csv文件->下一步选择导入文件->下一步设置分隔符->下一步设置字段名称，导入起始结束行 ->下一步设置源表目标表->设置字段 ->下一步选择导入模式->点击开始导入->导入成功
  

2、作业

• 项目七: 各部门工资最高的员工（难度：中等）
  编写一个 SQL 查询，找出每个部门工资最高的员工。例如，根据上述给定的表格，Max 在 IT 部门有最高工资，Henry 在 Sales 部门有最高工资。

------------------------------------------------------------
-----**************项目七******************************-----
------------------------------------------------------------
CREATE TABLE employee (
id INT UNSIGNED AUTO_INCREMENT,
name VARCHAR(20) NOT NULL,
salary INT(10) NOT NULL,
departmentId INT UNSIGNED NOT NULL,
PRIMARY KEY(id)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO employee(name,salary,departmentId) VALUES("Joe",70000,1);
INSERT INTO employee(name,salary,departmentId) VALUES("Henry",80000,2);
INSERT INTO employee(name,salary,departmentId) VALUES("Sam",60000,2);
INSERT INTO employee(name,salary,departmentId) VALUES("Max",90000,1);CREATE TABLE department(
departmentId INT UNSIGNED AUTO_INCREMENT,
d_name VARCHAR(20) NOT NULL,
PRIMARY KEY(departmentId)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO department(d_name) VALUES('IT');
INSERT INTO department(d_name) VALUES('Sales');--GROUP BY 和MAX()函数不能直接一起用，GROUP BY返回的是小组第一行的值，MAX()返回的是最大的，2组值组合在一起，会有错误SELECT d.d_name,e.name,e.salary FROM employee e LEFT JOIN department d on e.departmentId=d.departmentId
where e.salary IN(SELECT MAX(salary)FROM employeeGROUP BY departmentId);

• 项目八: 换座位（难度：中等)
  小美是一所中学的信息科技老师，她有一张 seat 座位表，平时用来储存学生名字和与他们相对应的座位 id。
  其中纵列的 id 是连续递增的
  小美想改变相邻俩学生的座位。
  你能不能帮她写一个 SQL query 来输出小美想要的结果呢？

------------------------------------------------------------
-----**************项目八、换座位************************---
------------------------------------------------------------
CREATE TABLE seats(id INT UNSIGNED AUTO_INCREMENT,sname VARCHAR(40) NOT NULL,PRIMARY KEY(id)
)ENGINE= INNODB DEFAULT CHARSET=utf8;INSERT INTO seats(sname) VALUES("Abbot");
INSERT INTO seats(sname) VALUES("Doris");
INSERT INTO seats(sname) VALUES("Emerson");
INSERT INTO seats(sname) VALUES("Green");
INSERT INTO seats(sname) VALUES("Jeames"); SELECT (CASE WHEN id%2=1 and id = (SELECT COUNT(*) FROM seats) THEN idWHEN id%2 =1 THEN id+1ELSE id-1END) AS id,sname
FROM seats
ORDER BY id;

• 项目九: 分数排名（难度：中等）
  编写一个 SQL 查询来实现分数排名。如果两个分数相同，则两个分数排名（Rank）相同。请注意，平分后的下一个名次应该是下一个连续的整数值。换句话说，名次之间不应该有“间隔”。

------------------------------------------------------------
-----**************项目九、分数排名************************--
------------------------------------------------------------
CREATE TABLE score (sco_id INT UNSIGNED AUTO_INCREMENT,score FLOAT NOT NULL,PRIMARY KEY(sco_id)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO score(score) VALUES(3.50);
INSERT INTO score(score) VALUES(3.65);
INSERT INTO score(score) VALUES(4.00);
INSERT INTO score(score) VALUES(3.50);
INSERT INTO score(score) VALUES(3.85);
INSERT INTO score(score) VALUES(4.00);
INSERT INTO score(score) VALUES(3.65);SELECT score,(SELECT COUNT(DISTINCT(score))+1FROM scoreWHERE Score>s1.Score
) AS RANK
FROM score AS s1
ORDER BY Score DESC,sco_id ASC;

3、MySQL 实战 - 复杂项目

• 项目十：行程和用户（难度：困难）

------------------------------------------------------------
-----*******项目十、行程和用户****************************--
------------------------------------------------------------
CREATE TABLE trips(
id INT UNSIGNED AUTO_INCREMENT,
client_id INT NOT NULL,
driver_id INT NOT NULL,
city_id INT NOT NULL,
status enum('completed','cancelled_by_driver','cancelled_by_client'),
request_at DATE NOT NULL,
PRIMARY KEY(id)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(1,10,1,'completed','2013-10-01');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(2,11,1,'cancelled_by_driver','2013-10-01');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(3,12,6,'completed','2013-10-01');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(4,13,6,'cancelled_by_client','2013-10-01');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(1,10,1,'completed','2013-10-02');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(2,11,6,'completed','2013-10-02');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(3,12,6,'completed','2013-10-02');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(2,12,12,'completed','2013-10-03');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(3,10,12,'completed','2013-10-03');
INSERT INTO trips(client_id,driver_id,city_id,status,request_at) VALUES(4,13,12,'cancelled_by_client','2013-10-03');CREATE table users (
userId INT UNSIGNED AUTO_INCREMENT,
banned VARCHAR(4) NOT NULL,
role enum('client','driver','partner'),
PRIMARY KEY(userId)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO users(banned,role) VALUES( "No",'client');
INSERT INTO users(banned,role) VALUES( "Yes",'client');
INSERT INTO users(banned,role) VALUES( "No",'client');
INSERT INTO users(banned,role) VALUES( "No",'client');
INSERT INTO users(banned,role) VALUES( "No",'driver');
INSERT INTO users(banned,role) VALUES( "No",'driver');
INSERT INTO users(banned,role) VALUES( "No",'driver');
INSERT INTO users(banned,role) VALUES( "No",'driver');SELECT t.request_at AS 'Day',
ROUND((SUM(CASE WHEN t.Status LIKE 'cancelled%' THEN 1 ELSE 0 END))/COUNT(*),2) AS 'Cancellation Rate'
FROM trips AS t INNER JOIN users AS u
ON u.userId = t.client_id AND u.banned = 'No'
GROUP BY t.request_at;

• 项目十一：各部门前3高工资的员工（难度：中等）
  将项目7中的employee表清空，重新插入以下数据（其实是多插入5,6两行）,编写一个 SQL 查询，找出每个部门工资前三高的员工。例如，根据上述给定的表格，查询结果应返回,此外，请考虑实现各部门前N高工资的员工功能。

CREATE TABLE employee (
id INT UNSIGNED AUTO_INCREMENT,
name VARCHAR(20) NOT NULL,
salary INT(10) NOT NULL,
departmentId INT UNSIGNED NOT NULL,
PRIMARY KEY(id)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO employee(name,salary,departmentId) VALUES("Joe",70000,1);
INSERT INTO employee(name,salary,departmentId) VALUES("Henry",80000,2);
INSERT INTO employee(name,salary,departmentId) VALUES("Sam",60000,2);
INSERT INTO employee(name,salary,departmentId) VALUES("Max",90000,1);
INSERT INTO employee(name,salary,departmentId) VALUES("Janet",69000,1);
INSERT INTO employee(name,salary,departmentId) VALUES("Randy",85000,1);

• 项目十二 分数排名 - （难度：中等）
  依然是昨天的分数表，实现排名功能，但是排名是非连续的，如下：
  +-------+------+
  | Score | Rank |
  +-------+------+
  | 4.00 | 1 |
  | 4.00 | 1 |
  | 3.85 | 3 |
  | 3.65 | 4 |
  | 3.65 | 4 |
  | 3.50 | 6 |
  +-------+------

CREATE TABLE score (sco_id INT UNSIGNED AUTO_INCREMENT,score FLOAT NOT NULL,PRIMARY KEY(sco_id)
)ENGINE=INNODB DEFAULT CHARSET=utf8;INSERT INTO score(score) VALUES(3.50);
INSERT INTO score(score) VALUES(3.65);
INSERT INTO score(score) VALUES(4.00);
INSERT INTO score(score) VALUES(3.50);
INSERT INTO score(score) VALUES(3.85);
INSERT INTO score(score) VALUES(4.00);
INSERT INTO score(score) VALUES(3.65);