create database one20210605 default charset=utf8;
use one20210605;
create table student(
sid int , # 學(xué)生的id
`name`varchar(10), # 學(xué)生姓名
saddress varchar(100) # 學(xué)生地址
);
create table course (
cid int , # 課程id
sid int , # 選課的學(xué)生id
cname varchar(100) # 課程的名字
);
insert into student values (1 ,"關(guān)羽","許昌"),(2,"孔明","南陽"),(3,"張飛","河北"),(4,"劉備","四川"),(5,"阿斗","蜀國");
insert into course values ( 101 , 1 ,"三百回合不累法"),(102,2,"勸人投降話術(shù)"),(101,3,"三百回合不累法"),(102,4,"勸人投降話術(shù)"),(103,6,"如何俘獲大喬和小喬");
select * from student;
select * from course;
-- 交叉查詢 (笛卡爾積查詢)
select * from student , course;
select * from student , course where student.sid = course.sid;
-- 內(nèi)連接
select * from student inner join course on student.sid=course.sid;
-- 左外連接
select * from student left join course on student.sid = course.sid;
