/*多表查询*/
/*交叉连接*(表1条数*表2条数)*/
SELECT * FROM emp JOIN dept;
/*内连接(在交叉连接基础上加条件）*/
SELECT * FROM emp JOIN dept ON deptid=id;
SELECT * FROM emp JOIN dept ON emp.deptid=dept.id;
/*左外连接*(以左表为主表)*/；
SELECT * FROM product_type LEFT JOIN product ON product.`protype_id`=product_type.`protype_id`;
/*右外连接*(以右表为主表)*/；
SELECT * FROM product_type RIGHT JOIN product ON product.`protype_id`=product_type.`protype_id`;
/*子查询：把一个查询结果当作另一个查询的条件*/
/*找出索尼手机所属类别*/
SELECT protype_id FROM product WHERE pro_name LIKE \'%索尼%4G手机%\';
SELECT protype_name FROM product_type WHERE protype_id=(
SELECT protype_id FROM product WHERE pro_name LIKE \'%索尼%4G手机%\'
);
/*找出所有属于手机数码的产品*/
SELECT * FROM product WHERE protype_id=(
SELECT protype_id FROM product_type WHERE protype_name=\'手机数码\'
);
/*找出所有属于手机数码或者电脑办公的产品*/
SELECT protype_id FROM product_type WHERE protype_name=\'手机数码\' OR protype_name=\'电脑办公\';
SELECT * FROM product WHERE protype_id IN(
SELECT protype_id FROM product_type WHERE protype_name=\'手机数码\' OR protype_name=\'电脑办公\'
);
/*联合查询*/
CREATE TABLE app1(
aid INT PRIMARY KEY AUTO_INCREMENT,
aname VARCHAR(10),
adesc VARCHAR(50)
);
CREATE TABLE bpp1(
bid INT PRIMARY KEY AUTO_INCREMENT,
bname VARCHAR(10),
bdesc VARCHAR(50)
);
INSERT INTO app1(aname,adesc) VALUES(\'熊大\',\'保护森林\');
INSERT INTO app1(aname,adesc) VALUES(\'光头强\',\'砍树\');
INSERT INTO bpp1(bname,bdesc) VALUES(\'小红帽\',\'傻吊\');
INSERT INTO bpp1(bname,bdesc) VALUES(\'大灰狼\',\'牛逼\');
SELECT aid,adesc FROM app1
UNION
SELECT bname,bdesc FROM bpp1;
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