連接查詢是關(guān)系型數(shù)據(jù)庫中最主要的查，主要包括內(nèi)連接、外連接可以實(shí)現(xiàn)多個(gè)表查詢。

下面創(chuàng)建兩張表演示幾種連接查詢

學(xué)生表

CREATE TABLE student( id BIGINT(20) NOT NULL AUTO_INCREMENT,name VARCHAR(30),address VARCHAR(100),PRIMARY KEY(id) ) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;INSERT INTO student(name,address) VALUES('小明','北京市'); INSERT INTO student(name,address) VALUES('小紅','上海市'); INSERT INTO student(name,address) VALUES('小東','深圳市'); INSERT INTO student(name,address) VALUES('小麗','杭州市'); INSERT INTO student(name,address) VALUES('小智','南京市'); INSERT INTO student(name,address) VALUES('小林','天津市'); select * from student;

成績表

CREATE TABLE chengji( id BIGINT(20) NOT NULL AUTO_INCREMENT,student_id BIGINT(20) NOT NULL,socre FLOAT(5,2),PRIMARY KEY(id) ) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;INSERT INTO chengji(student_id,socre) VALUES(1,95.54); INSERT INTO chengji(student_id,socre) VALUES(2,124.4); INSERT INTO chengji(student_id,socre) VALUES(3,130.0); INSERT INTO chengji(student_id,socre) VALUES(4,135.22); INSERT INTO chengji(student_id,socre) VALUES(5,149.547); select * from chengji;

內(nèi)連接

select * from student a inner join chengji b on a.id = b.student_id;

外連接

左外連接

select * from student a left join chengji b on a.id = b.student_id;

右外連接

select * from student a right join chengji b on a.id = b.student_id;

轉(zhuǎn)載于:https://www.cnblogs.com/tkzL/p/11609631.html

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