--創(chuàng)建數(shù)據(jù)庫(文件：主要數(shù)據(jù)文件mdf==1，次要數(shù)據(jù)文件ndf>=0，日志文件ldf>=1)
--文件組：當(dāng)1mdf,5個ndf(1,2,2),10個ldf(3,3,4),將它們分成多個組存放
CREATE database studb;
--創(chuàng)建表teacher,student
create table teacher
(
tid int(10) primary key auto_increment,
tname varchar(20),
tage int(10)
);
use studb;
create table student
(
sid int(10) primary key auto_increment,
sname varchar(20),
sage int(10),
tid int(10) REFERENCES teacher(tid)
);
--外鍵約束：你問張三的老師是誰？？
--select teacher.tname from teacher,student where student.sname = '張三'
select t.tname from teacher t,student s where s.sname = '張三' and t.tid = s.tid
--創(chuàng)建課程表
create table course
(
cid int(10) primary key,
cname varchar(20),
tid int(10) REFERENCES teacher(tid)
);
--創(chuàng)建分?jǐn)?shù)表
create table sc
(
scid int(10) primary key,
sid int(10) REFERENCES student(sid),
cid int(10) REFERENCES course(cid),
score int(10)
);
--聯(lián)合查詢：等值查詢
--1..
select c.cname from course c,student s,sc where s.sname = '小張'
and s.sid = sc.sid and c.cid = sc.cid;
--2..
select sname from student s,course c,sc where c.cname='android' and sc.score>=60
and s.sid = sc.sid and c.cid = sc.cid;
--3..
--子查詢：當(dāng)條件也要查詢的時候,我只知道學(xué)號，我不知道"小張"這個字段,那你知道小張的學(xué)號 嗎
delete from sc where sid = (select sid from student where sname = '小張');
--子查詢中間的符號一定是父查詢與子查詢兩張表關(guān)聯(lián)的字段(一般是主外鍵)
--4..
update sc set score=score+5 where cid=????;
select tid from teacher where tname='李老師' ==1
select cname from course where tid = 1 ==課程名字，李老師教的
select cid from course where cname='android' ==課程ID
update sc set score=score+5 where cid=
(
select cid from course where cname=
(
select cname from course where tid =
(
select tid from teacher where tname='李老師'
)
)
);
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