首先公布一下DAY6的作业答案。
项目九:
--code--
--建表并插入数据
CREATE TABLE IF NOT EXISTS Trips (
Id INT,
Client_Id INT,
Driver_Id INT,
City_Id INT,
Status ENUM('completed', 'cancelled_by_driver', 'cancelled_by_client'),
Request_at VARCHAR(50)
);
CREATE TABLE IF NOT EXISTS Users (
Users_Id INT,
Banned VARCHAR(50),
Role ENUM('client', 'driver', 'partner')
);
TRUNCATE TABLE Trips;
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('1', '1', '10', '1', 'completed', '2013-10-01');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('2', '2', '11', '1', 'cancelled_by_driver', '2013-10-01');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('3', '3', '12', '6', 'completed', '2013-10-01');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('4', '4', '13', '6', 'cancelled_by_client', '2013-10-01');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('5', '1', '10', '1', 'completed', '2013-10-02');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('6', '2', '11', '6', 'completed', '2013-10-02');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('7', '3', '12', '6', 'completed', '2013-10-02');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('8', '2', '12', '12', 'completed', '2013-10-03');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('9', '3', '10', '12', 'completed', '2013-10-03');
INSERT INTO Trips (Id, Client_Id, Driver_Id, City_Id, Status, Request_at) VALUES ('10', '4', '13', '12', 'cancelled_by_driver', '2013-10-03');
TRUNCATE TABLE Users;
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('1', 'No', 'client');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('2', 'Yes', 'client');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('3', 'No', 'client');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('4', 'No', 'client');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('10', 'No', 'driver');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('11', 'No', 'driver');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('12', 'No', 'driver');
INSERT INTO Users (Users_Id, Banned, Role) VALUES ('13', 'No', 'driver');
--
mysql> SELECT
-> Request_at AS Day,
-> FORMAT(sum(IF(Status LIKE 'cancelled%', 1, 0))/count(1), 2) AS 'Cancellation Rate'
-> FROM Trips as t
-> inner join Users as u on t.Client_Id = u.Users_Id
-> where u.Banned = 'NO'
-> GROUP BY Day;
+------------+-------------------+
| Day | Cancellation Rate |
+------------+-------------------+
| 2013-10-01 | 0.33 |
| 2013-10-02 | 0.00 |
| 2013-10-03 | 0.50 |
+------------+-------------------+
3 rows in set (0.00 sec)
项目十:
--code--
mysql> set @nn =3; --设置前N高变量nn--
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT d.`Name` AS Department,e1.`Name` AS Employee,e1.Salary AS Salary
-> FROM employee e1
-> JOIN department d
-> ON e1.DepartmentId = d.id
-> WHERE (
-> SELECT COUNT(DISTINCT e2.Salary)
-> FROM employee e2
-> WHERE e2.Salary > e1.Salary AND e1.DepartmentId = e2.DepartmentId
-> ) < @nn --使用参数nn--
-> ORDER BY d.`Name`,e1.Salary desc;
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT | Max | 90000 |
| IT | Randy | 85000 |
| IT | Joe | 70000 |
| Sales | Henry | 80000 |
| Sales | Sam | 60000 |
+------------+----------+--------+
5 rows in set (0.00 sec)
项目十一:
--code--
mysql> SELECT FORMAT(Score,2) as Score,
-> (SELECT count(*) FROM scores AS s2 WHERE s2.Score > s1.Score)+1 AS Rank
-> FROM scores AS s1
-> ORDER BY Score DESC;
+-------+------+
| Score | Rank |
+-------+------+
| 4.00 | 1 |
| 4.00 | 1 |
| 3.85 | 3 |
| 3.65 | 4 |
| 3.65 | 4 |
| 3.50 | 6 |
+-------+------+
6 rows in set (0.00 sec)