Question

我有这个庞大的数据库：

#
# Dropping tables
#

DROP TABLE IF EXISTS hotels;
DROP TABLE IF EXISTS guests;
DROP TABLE IF EXISTS rooms;
DROP TABLE IF EXISTS reservation;

#
# Table structure for tables hotels, guests, rooms and reservation
#

CREATE TABLE hotels(
hotel_code int(4) unsigned NOT NULL default '0',
hotel_name char(20) default NULL,
city char(20) default NULL,
address char(20) default NULL,
hotel_rank int(1) unsigned NOT NULL default '0',
phone char(10) default NULL,
number_of_rooms int(4) unsigned NOT NULL default '0',
PRIMARY KEY  (hotel_code));

CREATE TABLE guests(
id char(10) default NULL,
name char(20) default NULL,
city char(20) default NULL,
address char(20) default NULL,
state char(20) default NULL,
PRIMARY KEY  (id));

CREATE TABLE rooms(
hotel_code int(4) unsigned NOT NULL default '0',
room_number int(4) unsigned NOT NULL default '0',
type char(20) default NULL,
beds int(4) unsigned NOT NULL default '0',
price int(4) unsigned NOT NULL default '0',
PRIMARY KEY  (hotel_code, room_number));

CREATE TABLE reservation(
hotel_code int(4) unsigned NOT NULL default '0',
room_number int(4) unsigned NOT NULL default '0',
from_date char(20) default NULL,
to_date char(20) default NULL,
payment_method char(20) default NULL,
id char(10) default NULL,
PRIMARY KEY  (hotel_code, room_number, from_date));

#
# Dumping data for tables hotels, guests, rooms and reservation
#

INSERT INTO hotels VALUES
(1, 'Meridian', 'Tel Aviv', 'Shinkin 24', 3, '03-6527384', 230),
(2, 'Meridian', 'Tveria', 'Kineret 22', 5, '04-7369944', 320),
(3, 'King David', 'Jerusalem', 'Kineret 22', 5, '02-7435334', 200),
(4, 'Hilton', 'Jerusalem', 'Kineret 22', 4, '02-4566324', 180),
(5, 'Herods', 'Eilat', 'Dolphin 14', 4, '09-7333245', 190),
(6, 'Hof Yam', 'Haifa', 'Kasam 39', 5, '04-7344545', 150),
(7, 'Ha Tsuk', 'Haifa', 'Lohem 17', 3, '04-7345678', 110),
(8, 'Ha Nesiha', 'Eilat', 'Suf 4', 5, '09-6543543', 170),
(9, 'King David', 'Tveria', 'Kineret 55', 5, '04-7445544', 270);

INSERT INTO guests VALUES
('00000001-0', 'Adam', 'Gan Eden', 'Mango 3', 'Israel'),
('00000002-0', 'Eve', 'Gan Eden', 'Avucado 12', 'Israel'),
('04352244-4', 'Dani Mor', 'Tel Aviv', 'Magen 3', 'Israel'),
('06112343-6', 'Amiad Rozenberg', 'Petah Tikva', 'Zahal 14', 'Israel'),
('12345678-0', 'Ehud Olmert', 'Jerusalem', 'Money 99', 'Israel'),
('87654321-0', 'Moris Talenski', 'Jerusalem', 'Money 100', 'Israel'),
('04256372-0', 'Uri Meser', 'Holyland', 'Money 101', 'Israel'),
('02637482-0', 'Shula Zaken', 'Jerusalem', 'Money 102', 'Israel'),
('00000000-0', 'Gimel', 'Mosad', 'Secret 007', 'Dubai');

INSERT INTO rooms VALUES
(1, 100, 'basic', 2, 100),
(1, 101, 'basic', 2, 100),
(1, 102, 'basic', 2, 100),
(1, 200, 'double', 2, 100),
(1, 201, 'double', 2, 100),
(1, 202, 'double', 2, 100),
(1, 300, 'truple', 3, 180),
(1, 400, 'honeymoon', 2, 270),
(2, 100, 'basic', 2, 100),
(2, 200, 'double', 4, 200),
(2, 201, 'double', 4, 200),
(2, 202, 'double', 4, 200),
(2, 300, 'truple', 5, 220),
(2, 400, 'honeymoon', 3, 230),
(2, 401, 'honeymoon', 3, 230),
(3, 100, 'basic', 2, 100),
(3, 200, 'double', 2, 210),
(3, 201, 'double', 2, 210),
(3, 202, 'double', 2, 210),
(3, 300, 'truple', 4, 220),
(3, 400, 'honeymoon', 3, 230),
(4, 100, 'basic', 2, 100),
(4, 200, 'double', 1, 500),
(4, 300, 'truple', 4, 120),
(4, 301, 'truple', 4, 120),
(4, 400, 'honeymoon', 3, 230),
(4, 401, 'honeymoon', 3, 230),
(4, 402, 'honeymoon', 3, 230),
(4, 403, 'honeymoon', 3, 230),
(5, 100, 'basic', 2, 100),
(5, 200, 'double', 4, 150),
(5, 300, 'truple', 4, 340),
(5, 400, 'honeymoon', 3, 210),
(6, 100, 'basic', 2, 100),
(6, 101, 'basic', 2, 100),
(6, 200, 'double', 3, 110),
(6, 201, 'double', 3, 110),
(6, 300, 'truple', 4, 310),
(6, 400, 'honeymoon', 1, 240),
(7, 100, 'basic', 2, 100),
(7, 101, 'basic', 2, 100),
(7, 102, 'basic', 2, 100),
(7, 200, 'double', 4, 130),
(7, 300, 'truple', 2, 250),
(7, 301, 'truple', 2, 250),
(7, 302, 'truple', 2, 250),
(7, 400, 'honeymoon', 3, 280),
(8, 100, 'basic', 2, 90),
(8, 200, 'double', 4, 290),
(8, 300, 'truple', 2, 430),
(8, 400, 'honeymoon', 3, 150),
(9, 100, 'basic', 2, 130),
(9, 200, 'double', 4, 150),
(9, 300, 'truple', 2, 280),
(9, 400, 'honeymoon', 3, 270);

INSERT INTO reservation VALUES
(6, 300, '2010-06-15', '2010-06-29', 'cash', '00000001-0'),
(5, 400, '2010-01-02', '2010-01-13', 'credit', '00000001-0'),
(4, 300, '2010-06-15', '2010-07-01', 'cash', '00000002-0'),
(5, 400, '2010-01-01', '2010-01-13', 'credit', '00000002-0'),
(3, 200, '2010-06-15', '2010-08-01', 'cash', '04352244-4'),
(2, 100, '2010-04-15', '2010-06-21', 'cash', '06112343-6'),
(1, 100, '2010-06-23', '2010-07-01', 'cash', '06112343-6'),
(8, 300, '2010-04-12', '2010-04-15', 'cash', '12345678-0'),
(8, 200, '2010-04-12', '2010-04-15', 'cash', '87654321-0'),
(8, 100, '2010-04-12', '2010-04-15', 'cash', '04256372-0'),
(8, 200, '2010-04-17', '2010-04-25', 'cash', '04256372-0'),
(8, 200, '2010-04-25', '2010-04-29', 'cash', '02637482-0');

我想写一下查询：

present a list of the hotels with more than 2 rooms , where their price is 
bigger than 186 . 
Order it by : hotel name ,city ,number of rooms . Sort by number of rooms .

所以我的查询是：

SELECT DISTINCT hotel_name, city, rooms_number
FROM hotels JOIN
(SELECT DISTINCT hotel_code, COUNT(*) as rooms_number
FROM rooms
WHERE price > 186
GROUP BY hotel_code
) as rooms_count
ON (hotels.hotel_code = rooms_count.hotel_code AND rooms_number > 2)
ORDER BY rooms_number;

但是这个查询太长了，是不是可以用另一种方式写它符合问题的需要？

Answer 1

您可以使用HAVING子句来避免子选择。

SELECT
    a.hotel_name,
    a.city,
    COUNT(*) AS room_count
FROM 
    hotels a
INNER JOIN
    rooms b ON a.hotel_code = b.hotel_code AND b.price > 186
GROUP BY
    a.hotel_name,
    a.city
HAVING
    COUNT(*) > 2
ORDER BY
    room_count DESC

如何以简短而优雅的方式编写SQL查询？

1 个答案: