Test data:
the Suppliers
CREATE TABLE suppliers(
s_id INT NOT NULL AUTO_INCREMENT,
s_name CHAR(50) NOT NULL,
s_city CHAR(10) NULL,
s_zip CHAR(10) NULL,
s_call CHAR(50) NOT NULL,
PRIMARY KEY(s_id)
);
INSERT INTO suppliers(s_id, s_name,s_city, s_zip, s_call)
VALUES(101,'FastFruit Inc.','Tianjin','300000','48075'),
(NULL,'LT Supplies','Chongqing','400000','44333'),
(NULL,'ACME','Shanghai','200000','90046'),
(NULL,'FNK Inc.','Zhongshan','528437','11111'),
(NULL,'Good Set','Taiyuang','030000', '22222'),
(NULL,'Just Eat Ours','Beijing','010', '45678'),
(NULL,'DK Inc.','Zhengzhou','450000', '33332');
fruits
CREATE TABLE fruits
(
f_id char(10) NOT NULL,
s_id INT NOT NULL,
f_name char(255) NOT NULL,
f_price decimal(8,2) NOT NULL,
PRIMARY KEY(f_id)
);
INSERT INTO fruits (f_id, s_id, f_name, f_price)
VALUES('a1', 101,'apple',5.2),
('b1',101,'blackberry', 10.2),
('bs1',102,'orange', 11.2),
('bs2',105,'melon',8.2),
('t1',102,'banana', 10.3),
('t2',102,'grape', 5.3),
('o2',103,'coconut', 9.2),
('c0',101,'cherry', 3.2),
('a2',103, 'apricot',2.2),
('l2',104,'lemon', 6.4),
('b2',104,'berry', 7.6),
('m1',106,'mango', 15.6),
('m2',105,'xbabay', 2.6),
('t4',107,'xbababa', 3.6),
('m3',105,'xxtt', 11.6),
('b5',107,'xxxx', 3.6);
Table Structure:
Fruit
f_id s_id f_name f_price
------ ------ ---------- ---------
a1 101 apple 5.20
a2 103 apricot 2.20
b1 101 blackberry 10.20
b2 104 berry 7.60
b5 107 xxxx 3.60
bs1 102 orange 11.20
bs2 105 melon 8.20
c0 101 cherry 3.20
l2 104 lemon 6.40
m1 106 mango 15.60
m2 105 xbabay 2.60
m3 105 xxtt 11.60
o2 103 coconut 9.20
t1 102 banana 10.30
t2 102 grape 5.30
t4 107 xbababa 3.60
suppliers
s_id s_name s_city s_zip s_call
------ -------------- --------- ------ --------
101 FastFruit Inc. Tianjin 300000 48075
102 LT Supplies Chongqing 400000 44333
103 ACME Shanghai 200000 90046
104 FNK Inc. Zhongshan 528437 11111
105 Good Set Taiyuang 030000 22222
106 Just Eat Ours Beijing 010 45678
107 DK Inc. Zhengzhou 450000 33332
- Inner join query
SELECT suppliers.`s_id`,s_name,f_name,f_price
FROM fruits,suppliers
WHERE fruits.`s_id`=suppliers.`s_id`;
Table as fruits and suppliers Table s_id have the same field, so when the comparison, the table needs to fully qualified name (the format of "table name, column name"), is given only if the s_id, MySQL will not know which refers to a, and returns an error message.
- inner join
SELECT suppliers.`s_id`,s_name,f_name,f_price
FROM fruits inner join suppliers
on fruits.`s_id`=suppliers.`s_id`;
Query supply f_id = 'a1' fruit-supplied types of fruit and fruit vendor's name
select f.`f_name`,s.`s_name`
from fruits as f inner join suppliers as s on f.`s_id`=s.`s_id`
where f.`s_id`=(select s_id from fruits as f where f.`f_id`='a1')；
inner join XXXX on XXXX where XXXX
- self-join
query supply f_id = 'a1' of the type provided by Fruit Fruit
select f.`f_name` from fruits as f , fruits as r
where f.`s_id`=r.s_id and r.f_id='a1';
Note: select sub-query
SELECT f.`f_name`
FROM fruits AS f
WHERE f.`s_id`=(SELECT s_id FROM fruits AS f WHERE f.`f_id`='a1')
