内连接3表
我的数据库中有6个表 
.现在我想加入car_space,transaction和sport_facilities.但是,我遇到了问题.
当我分别使用这两个sql命令时,这些命令也可以运行,我可以得到我想要的结果.
-- car_space INNER JOIN transaction
SELECT * FROM car_space INNER JOIN transaction ON car_space.carSpaceId = transaction.carSpaceId ORDER BY transactionId;
-- sport_facilities INNER JOIN transaction
SELECT * FROM sport_facilities INNER JOIN transaction ON sport_facilities.sportFacilitiesId = transaction.sportFacilitiesId ORDER BY transactionId;
然后,我将它们组合成一个命令.
-- Combine But Not Work
SELECT * FROM transaction
INNER JOIN car_space ON transaction.carSpaceId = car_space.carSpaceId
INNER JOIN sport_facilities ON transaction.sportFacilitiesId = sport_facilities.sportFacilitiesId
ORDER BY transactionId;
虽然可以运行,但没有显示结果或记录.
我想做的是当我输入transactionId时,可以在数据库中找到记录表(car_space/sport_facilities).例如:我输入WHERE transactionId = 1
数据库可以搜索这是来自sport_facilities表而不是car_space.
谢谢.这是一些供参考的代码.
-- Create a database
CREATE DATABASE booking_system;
-- Use This database
USE booking_system;
-- Create smartcart table
CREATE TABLE card(
cardId CHAR(8) NOT NULL,
PRIMARY KEY (cardId)
);
-- Insert some recond to card table
INSERT INTO card VALUES
('4332A0D5'),
('637ED500'),
('B3895A02'),
('E32F3702')
;
-- Create user table
CREATE TABLE user(
userId INT(5) NOT NULL AUTO_INCREMENT,
cardNo CHAR(8) NOT NULL,
firstName VARCHAR(255) NOT NULL,
lastName VARCHAR(255) NOT NULL,
sex CHAR(1) NOT NULL,
dob DATE NOT NULL,
hkid CHAR(8) NOT NULL,
email VARCHAR(255) NOT NULL,
telNo INT(8) NOT NULL,
PRIMARY KEY (userId),
FOREIGN KEY (cardNo) REFERENCES card (cardId) ON DELETE CASCADE,
UNIQUE (hkid)
);
-- Alter user table
ALTER TABLE user AUTO_INCREMENT = 16001;
-- Insert some recond to user table
INSERT INTO user VALUES
('','4332A0D5','Andy','Ding','M','1962-04-20','K5216117','mkding@yahoo.com','98626229'),
('','637ED500','Emma','Dai','F','1972-06-15','D5060339','emmadai@yahoo.com.hk','62937453'),
('','B3895A02','Brinsley','Au','F','1984-02-24','P8172327','da224@live.hk','91961624'),
('','E32F3702','Eric','Fong','M','1990-04-15','Y1129323','ericfong0415@gmail.com','98428731')
;
-- Create car space price table
CREATE TABLE car_space_price(
spaceNo INT(2) NOT NULL AUTO_INCREMENT,
price INT(2) NOT NULL,
carSpaceDescription VARCHAR(16),
CHECK (carSpaceDescription IN ('motorcycles','small vehicles','medium vehicles','large vehicles')),
PRIMARY KEY (spaceNo)
);
-- Insert some recond to car space price table
INSERT INTO car_space_price VALUES
('','10','motorcycles'), -- 1
('','10','motorcycles'), -- 2
('','10','motorcycles'), -- 3
('','10','motorcycles'), -- 4
('','10','motorcycles'), -- 5
('','20','small vehicles'), -- 6
('','20','small vehicles'), -- 7
('','20','small vehicles'), -- 8
('','20','small vehicles'), -- 9
('','20','small vehicles'), -- 10
('','40','medium vehicles'), -- 11
('','40','medium vehicles'), -- 12
('','40','medium vehicles'), -- 13
('','80','large vehicles'), -- 14
('','80','large vehicles') -- 15
;
-- Create car space table
CREATE TABLE car_space(
carSpaceId INT(5) NOT NULL AUTO_INCREMENT,
spaceNo INT(2) NOT NULL,
cardNo VARCHAR(8) NOT NULL,
inTime DATETIME,
outTime DATETIME,
PRIMARY KEY (carSpaceId),
FOREIGN KEY (spaceNo) REFERENCES car_space_price (spaceNo) ON DELETE CASCADE,
FOREIGN KEY (cardNo) REFERENCES card (cardId) ON DELETE CASCADE
);
-- Insert some recond to car space table
INSERT INTO car_space VALUES
('','2','E32F3702','2015-02-23 14:24:18','2015-02-23 17:01:43'), -- 1 --16004
('','6','B3895A02','2016-02-24 11:56:43','2016-02-25 09:21:08'), -- 2 --16003
('','2','E32F3702','2016-02-24 16:42:34','2016-02-24 21:02:45'), -- 3 --16004
('','2','E32F3702','2016-02-25 14:25:32','2016-02-25 17:03:54'), -- 4 --16004
('','6','B3895A02','2016-02-25 17:12:11','2016-02-25 20:58:18'), -- 5 --16003
('','13','637ED500','2016-02-25 19:17:03','2016-02-27 18:05:28'), -- 6 --16002
('','6','B3895A02','2016-02-25 21:14:03','2016-02-25 23:53:28'), -- 7 --16003
('','6','B3895A02','2016-02-26 08:46:23','2016-02-26 17:21:08'), -- 8 --16003
('','2','E32F3702','2016-02-26 14:15:45','2016-02-26 21:01:15'), -- 9 --16004
('','6','B3895A02','2016-02-27 09:42:13','2016-02-27 15:48:45'), -- 10 --16003
('','2','E32F3702','2016-02-27 13:25:45','2016-02-27 15:15:45'), -- 11 --16004
('','6','B3895A02','2016-02-28 10:57:16','2016-02-28 14:41:25'), -- 12 --16003
('','2','E32F3702','2016-02-28 11:47:32','2016-02-28 13:43:15'), -- 13 --16004
('','13','637ED500','2016-02-28 13:04:43','2016-03-02 22:39:46'), -- 14 --16002
('','2','E32F3702','2016-02-28 14:42:34','2016-02-28 21:47:45'), -- 15 --16004
('','6','B3895A02','2016-02-29 08:50:42','2016-02-29 14:28:42'), -- 16 --16003
('','2','E32F3702','2016-02-29 12:12:35','2016-02-29 16:45:28'), -- 17 --16004
('','6','B3895A02','2016-03-01 11:26:43','2016-03-01 14:56:26'), -- 18 --16003
('','6','B3895A02','2016-03-03 13:45:26','2016-03-03 17:54:18') -- 19 --16003
;
-- Create sport facilities price table
CREATE TABLE sport_facilities_price(
sportNo INT(2) NOT NULL AUTO_INCREMENT,
sportType VARCHAR(10) NOT NULL,
price INT(2) NOT NULL,
sportDescription VARCHAR(20),
PRIMARY KEY (sportNo)
);
-- Insert some recond to sport facilities price table
INSERT INTO sport_facilities_price VALUES
('','snooker','15','Snooker Room 1'), -- 1
('','snooker','15','Snooker Room 2'), -- 2
('','snooker','15','Snooker Room 3'), -- 3
('','snooker','15','Snooker Room 4'), -- 4
('','table_tennis','15','Table Tennis Room 1'), -- 5
('','table_tennis','15','Table Tennis Room 2'), -- 6
('','table_tennis','15','Table Tennis Room 3'), -- 7
('','table_tennis','15','Table Tennis Room 4'), -- 8
('','tennis','30','Tennis Vanue 1'), -- 9
('','tennis','30','Tennis Vanue 2'), -- 10
('','badminton','30','Badminton Vanue 1'), -- 11
('','badminton','30','Badminton Vanue 2'), -- 12
('','basketball','60','Hall') -- 13
;
-- Create sport facilities table
CREATE TABLE sport_facilities(
sportFacilitiesId INT(5) NOT NULL AUTO_INCREMENT,
sportNo INT(2) NOT NULL,
cardNo VARCHAR(8) NOT NULL,
bookDate DATE NOT NULL,
startTime TIME NOT NULL,
endTime TIME NOT NULL,
PRIMARY KEY (sportFacilitiesId),
FOREIGN KEY (sportNo) REFERENCES sport_facilities_price (sportNo) ON DELETE CASCADE,
FOREIGN KEY (cardNo) REFERENCES card (cardId) ON DELETE CASCADE
);
-- Insert some recond to sport facilities table
INSERT INTO sport_facilities VALUES
('','1','E32F3702','2015-02-23','12:00:00','14:00:00'), -- 1 --16004
('','5','B3895A02','2016-02-23','14:00:00','15:00:00'), -- 2 --16003
('','8','637ED500','2016-02-23','17:00:00','21:00:00'), -- 3 --16002
('','2','E32F3702','2016-02-24','09:00:00','11:00:00'), -- 4 --16004
('','5','4332A0D5','2016-02-24','13:00:00','14:00:00'), -- 5 --16001
('','7','637ED500','2016-02-24','15:00:00','17:00:00'), -- 6 --16002
('','8','B3895A02','2016-02-24','16:00:00','18:00:00'), -- 7 --16003
('','10','4332A0D5','2016-02-25','09:00:00','10:00:00'), -- 8 --16001
('','12','B3895A02','2016-02-25','13:00:00','14:00:00'), -- 9 --16003
('','6','637ED500','2016-02-25','21:00:00','22:00:00'), -- 10 --16002
('','4','637ED500','2016-02-26','11:00:00','13:00:00'), -- 11 --16002
('','8','4332A0D5','2016-02-26','22:00:00','23:00:00'), -- 12 --16001
('','13','B3895A02','2016-02-27','09:00:00','14:00:00'), -- 13 --16003
('','4','637ED500','2016-02-28','12:00:00','14:00:00'), -- 14 --16002
('','3','B3895A02','2016-02-28','14:00:00','15:00:00'), -- 15 --16003
('','4','E32F3702','2016-02-28','17:00:00','19:00:00'), -- 16 --16004
('','5','B3895A02','2016-02-28','21:00:00','22:00:00'), -- 17 --16003
('','2','4332A0D5','2016-02-28','21:00:00','23:00:00'), -- 18 --16001
('','10','E32F3702','2016-02-28','19:00:00','20:00:00'), -- 19 --16004
('','11','B3895A02','2016-02-29','11:00:00','13::00:00'), -- 20 --16003
('','8','E32F3702','2016-02-29','12:00:00','14:00:00'), -- 21 --16004
('','4','4332A0D5','2016-02-29','15:00:00','18:00:00'), -- 22 --16001
('','6','E32F3702','2016-03-01','09:00:00','11:00:00'), -- 23 --16004
('','5','637ED500','2016-03-01','12:00:00','15:00:00'), -- 24 --16002
('','3','B3895A02','2016-03-02','09:00:00','11:00:00'), -- 25 --16003
('','7','4332A0D5','2016-03-02','12:00:00','13:00:00'), -- 26 --16001
('','4','637ED500','2016-03-02','15:00:00','17:00:00'), -- 27 --16002
('','1','E32F3702','2016-03-02','19:00:00','22:00:00'), -- 28 --16004
('','12','4332A0D5','2016-03-03','11:00:00','13:00:00'), -- 29 --16001
('','9','E32F3702','2016-03-03','15:00:00','16:00:00'), -- 30 --16004
('','10','B3895A02','2016-03-03','09:00:00','11:00:00'), -- 31 --16003
('','4','637ED500','2016-03-04','11:00:00','12:00:00'), -- 32 --16002
('','8','E32F3702','2016-03-04','14:00:00','16:00:00'), -- 33 --16004
('','6','B3895A02','2016-03-05','19:00:00','21:00:00'), -- 34 --16003
('','13','E32F3702','2016-03-05','11:00:00','12:00:00'), -- 35 --16004
('','8','637ED500','2016-03-05','14:00:00','15:00:00'), -- 36 --16002
('','4','4332A0D5','2016-03-05','16:00:00','18:00:00'), -- 37 --16001
('','5','E32F3702','2016-03-06','13:00:00','15:00:00'), -- 38 --16004
('','9','B3895A02','2016-03-06','17:00:00','18:00:00'), -- 39 --16003
('','11','4332A0D5','2016-03-07','20:00:00','21::00:00'), -- 40 --16001
('','5','B3895A02','2016-03-07','22:00:00','23:00:00') -- 41 --16003
;
-- Create transaction table
CREATE TABLE transaction(
transactionId INT(5) UNSIGNED ZEROFILL NOT NULL AUTO_INCREMENT,
userId INT(5) NOT NULL,
carSpaceId INT(5),
sportFacilitiesId INT(5),
transactionDate DATE NOT NULL,
PRIMARY KEY (transactionId),
FOREIGN KEY (userId) REFERENCES user (userId) ON DELETE CASCADE,
FOREIGN KEy (carSpaceId) REFERENCES car_space (carSpaceId) ON DELETE CASCADE,
FOREIGN KEY (sportFacilitiesId) REFERENCES sport_facilities (sportFacilitiesId) ON DELETE CASCADE
);
-- Insert some recond to transaction table
INSERT INTO transaction VALUES
('','16004',NULL,'1','2015-02-23'), -- 1 -- Sport Facilities
('','16003',NULL,'5','2015-02-23'), -- 2 -- Sport Facilities
('','16004','2',NULL,'2015-02-23'), -- 3 -- Car Space
('','16002',NULL,'8','2015-02-23'), -- 4 -- Sport Facilities
('','16004',NULL,'2','2016-02-24'), -- 5 -- Sport Facilities
('','16003','6',NULL,'2016-02-24'), -- 6 -- Car Space
('','16001',NULL,'5','2016-02-24'), -- 7 -- Sport Facilities
('','16002',NULL,'7','2016-02-24'), -- 8 -- Sport Facilities
('','16003',NULL,'8','2016-02-24'), -- 9 -- Sport Facilities
('','16004','2',NULL,'2016-02-24'), -- 10 -- Car Space
('','16001',NULL,'10','2016-02-25'), -- 11 -- Sport Facilities
('','16003',NULL,'12','2016-02-25'), -- 12 -- Sport Facilities
('','16004','2',NULL,'2016-02-25'), -- 13 -- Car Space
('','16003','6',NULL,'2016-02-25'), -- 14 -- Car Space
('','16002','13',NULL,'2016-02-25'), -- 15 -- Car Space
('','16002',NULL,'6','2016-02-25'), -- 16 -- Sport Facilities
('','16003','6',NULL,'2016-02-25'), -- 17 -- Car Space
('','16003','6',NULL,'2016-02-26'), -- 18 -- Car Space
('','16002',NULL,'4','2016-02-26'), -- 19 -- Sport Facilities
('','16004','2',NULL,'2016-02-26'), -- 20 -- Car Space
('','16001',NULL,'8','2016-02-26'), -- 21 -- Sport Facilities
('','16003',NULL,'13','2016-02-27'), -- 22 -- Sport Facilities
('','16003','6',NULL,'2016-02-27'), -- 23 -- Car Space
('','16004','2',NULL,'2016-02-27'), -- 24 -- Car Space
('','16003','6',NULL,'2016-02-28'), -- 25 -- Car Space
('','16004','2',NULL,'2016-02-28'), -- 26 -- Car Space
('','16002',NULL,'4','2016-02-28'), -- 27 -- Sport Facilities
('','16002','13',NULL,'2016-02-28'), -- 28 -- Car Space
('','16003',NULL,'3','2016-02-28'), -- 29 -- Sport Facilities
('','16004','2',NULL,'2016-02-28'), -- 30 -- Car Space
('','16004',NULL,'4','2016-02-28'), -- 31 -- Sport Facilities
('','16003',NULL,'5','2016-02-28'), -- 32 -- Sport Facilities
('','16001',NULL,'2','2016-02-28'), -- 33 -- Sport Facilities
('','16004',NULL,'10','2016-02-28'), -- 34 -- Sport Facilities
('','16003','6',NULL,'2016-02-29'), -- 35 -- Car Space
('','16003',NULL,'11','2016-02-29'), -- 36 -- Sport Facilities
('','16004',NULL,'8','2016-02-29'), -- 37 -- Sport Facilities
('','16004','2',NULL,'2016-02-29'), -- 38 -- Car Space
('','16001',NULL,'4','2016-02-29'), -- 39 -- Sport Facilities
('','16004',NULL,'6','2016-03-01'), -- 40 -- Sport Facilities
('','16003','6',NULL,'2016-03-01'), -- 41 -- Car Space
('','16002',NULL,'5','2016-03-01'), -- 42 -- Sport Facilities
('','16003',NULL,'3','2016-03-02'), -- 43 -- Sport Facilities
('','16001',NULL,'7','2016-03-02'), -- 44 -- Sport Facilities
('','16002',NULL,'4','2016-03-02'), -- 45 -- Sport Facilities
('','16004',NULL,'1','2016-03-02'), -- 46 -- Sport Facilities
('','16001',NULL,'12','2016-03-03'), -- 47 -- Sport Facilities
('','16003','6',NULL,'2016-03-03'), -- 48 -- Car Space
('','16004',NULL,'9','2016-03-03'), -- 49 -- Sport Facilities
('','16003',NULL,'10','2016-03-03'), -- 50 -- Sport Facilities
('','16002',NULL,'4','2016-03-04'), -- 51 -- Sport Facilities
('','16004',NULL,'8','2016-03-04'), -- 52 -- Sport Facilities
('','16003',NULL,'6','2016-03-05'), -- 53 -- Sport Facilities
('','16004',NULL,'13','2016-03-05'), -- 54 -- Sport Facilities
('','16002',NULL,'8','2016-03-05'), -- 55 -- Sport Facilities
('','16001',NULL,'4','2016-03-05'), -- 56 -- Sport Facilities
('','16004',NULL,'5','2016-03-06'), -- 57 -- Sport Facilities
('','16003',NULL,'9','2016-03-06'), -- 58 -- Sport Facilities
('','16001',NULL,'11','2016-03-07'), -- 59 -- Sport Facilities
('','16003',NULL,'5','2016-03-07') -- 60 -- Sport Facilities
;
您希望如何组合行？
看起来您所有引用车位的交易都有 NULL 体育设施引用，反之亦然。
查询是逐行完成的，当您对车位进行 INNER JOIN 事务时，您将获得带有车位记录的所有事务记录以及车位引用。所有其他交易都被过滤掉。
由于这些过滤的事务 + 车位行都没有体育设施引用（全部为 NULL），因此当您将 INNER JOIN 添加到体育设施时，没有匹配的行，并且再次过滤掉不匹配的行。这会给您留下一个空的结果集。
要从双 INNER JOIN 查询返回任何结果，事务行必须引用（或链接）一个车位和一个体育设施。
如果您想保留所有交易行及其汽车空间或体育设施以及未引用的 NULL 记录，您可以将 INNER JOIN 更改为 LEFT JOIN（只需在最终查询中将 INNER 替换为 LEFT） 。
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