– 查看MySQL服務器所有數據庫
show databases;
– 刪除SRS數據庫
drop database if exists SRS;
– 創建學生選課系統(SRS)數據庫並指定默認字符集
create database SRS default charset utf8;
– 切換至SRS數據庫
use SRS;
– 查看當前數據庫中所有表
show tables;
– 創建學生表
create table TbStudent
(
stuid integer not null,
stuname varchar(20) not null,
stusex bit default 1,
stubirth datetime not null,
stutel char(11),
stuaddr varchar(255),
stuphoto longblob,
primary key (stuid)
);
– 修改學生表刪除stutel列
alter table TbStudent drop column stutel;
– 查看學生表結構
desc TbStudent;
– 如果表TbCourse已經存在就刪除它
drop table if exists TbCourse;
– 創建課程表
create table TbCourse
(
cosid integer not null,
cosname varchar(50) not null,
coscredit tinyint not null,
cosintro varchar(255)
);
– 給課程表指定主鍵
alter table TbCourse add constraint pk_course primary key (cosid);
– 創建學生選課記錄表
create table TbSC
(
scid integer primary key auto_increment,
sid integer not null,
cid integer,
scdate datetime not null,
score float
);
添加外鍵
alter table TbSC add foreign key (sid) references TbStudent (stuid) on delete cascade on update cascade;
alter table TbSC add foreign key (cid) references TBCourse (cosid) on delete set null on update cascade;
– 添加學生記錄
insert into TbStudent values (1001, '張三丰', default, '1978-1-1', '成都市一環路西二段17號', null);
insert into TbStudent (stuid, stuname, stubirth) values (1002, '郭靖', '1980-2-2');
insert into TbStudent (stuid, stuname, stusex, stubirth, stuaddr) values (1003, '黃蓉', 0, '1982-3-3', '成都市二環路南四段123號');
insert into TbStudent values (1004, '張無忌', 1, '1990-4-4', null, null);
insert into TbStudent values
(1005, '丘處機', 1, '1983-5-5', '北京市海淀區寶盛北里西區28號', null),
(1006, '王處一', 1, '1985-6-6', '深圳市寶安區寶安大道5010號', null),
(1007, '劉處玄', 1, '1987-7-7', '鄭州市金水區緯五路21號', null),
(1008, '孫不二', 0, '1989-8-8', '武漢市光谷大道61號', null),
(1009, '平一指', 1, '1992-9-9', '西安市雁塔區高新六路52號', null),
(1010, '老不死', 1, '1993-10-10', '廣州市天河區元崗路310號', null),
(1011, '王大錘', 0, '1994-11-11', null, null),
(1012, '隔壁老王', 1, '1995-12-12', null, null),
(1013, '郭嘯天', 1, '1977-10-25', null, null);
– 刪除學生記錄
delete from TbStudent where stuid=1004;
– 更新學生記錄
update TbStudent set stubirth='1980-12-12', stuaddr='上海市寶山區同濟支路199號' where stuid=1002;
– 添加課程記錄
insert into TbCourse values
(1111, 'C語言程序設計', 3, '大神級講師授課需要搶座'),
(2222, 'Java程序設計', 3, null),
(3333, '數據庫概論', 2, null),
(4444, '操作系統原理', 4, null);
– 添加學生選課記錄
insert into TbSC values
(default, 1001, 1111, '2016-9-1', 95),
(default, 1002, 1111, '2016-9-1', 94),
(default, 1001, 2222, now(), null),
(default, 1001, 3333, '2017-3-1', 85),
(default, 1001, 4444, now(), null),
(default, 1002, 4444, now(), null),
(default, 1003, 2222, now(), null),
(default, 1003, 3333, now(), null),
(default, 1005, 2222, now(), null),
(default, 1006, 1111, now(), null),
(default, 1006, 2222, '2017-3-1', 80),
(default, 1006, 3333, now(), null),
(default, 1006, 4444, now(), null),
(default, 1007, 1111, '2016-9-1', null),
(default, 1007, 3333, now(), null),
(default, 1007, 4444, now(), null),
(default, 1008, 2222, now(), null),
(default, 1010, 1111, now(), null);
– 查詢所有學生信息
select * from TbStudent;
– 查詢所有課程名稱及學分(投影和別名)
select cosname as `課程名稱`, coscredit as `學分` from TbCourse;
– 查詢所有女學生的姓名和出生日期(篩選)
select stuname, stubirth from TbStudent where stusex=0;
– 查詢所有80後學生的姓名、性別和出生日期(篩選)
select stuname as `姓名`, if(stusex, '男', '女') as `性別`, stubirth as `出生日期`
from TbStudent where stubirth between ‘1980-1-1’ and ‘1989-12-31’;
– 查詢姓王的學生姓名和性別(模糊)
select stuname, stusex from TbStudent where stuname like '王%';
– 查詢姓郭名字總共兩個字的學生的姓名(模糊)
select stuname from TbStudent where stuname like '郭_';
– 查詢姓郭名字總共三個字的學生的姓名(模糊)
select stuname from TbStudent where stuname like '郭__';
– 查詢名字中有王字的學生的姓名(模糊)
select stuname from TbStudent where stuname like '%王%';
– 查詢沒有錄入家庭住址和照片的學生姓名(多條件篩選和空值處理)
select stuname from TbStudent where stuaddr is null and stuphoto is null;
– 查詢學生選課的所有日期(去重)
select distinct scdate from TbSC;
– 查詢學生的姓名和生日按年齡從大到小排列(排序)
select stuname, stubirth from TbStudent order by stubirth;
– 查詢所有錄入了家庭住址的男學生的姓名、出生日期和家庭住址按年齡從小到大排列(多條件篩選和排序)
select stuname, stubirth, stuaddr from TbStudent where stusex=1 and stuaddr is not null order by stubirth desc;
– 查詢年齡最大的學生的出生日期(聚合函數)
select min(stubirth) from TbStudent;
– 查詢年齡最小的學生的出生日期(聚合函數)
select max(stubirth) from TbStudent;
– 查詢男女學生的人數(分組和聚合函數)
select if(stusex, '男', '女') as `性別`, count(stusex) as `人數` from TbStudent group by stusex;
– 查詢課程編號爲1111的課程的平均成績(篩選和聚合函數)
select avg(score) as `平均成績` from TbSC where cid=1111;
– 查詢學號爲1001的學生所有課程的總成績(篩選和聚合函數)
select sum(score) as `總成績` from TbSC where sid=1001;
– 查詢每個學生的學號和平均成績, null值處理成0(分組和聚合函數)
select sid as `學號`, ifnull(avg(score), 0) as `平均成績` from TbSC group by sid;
– 查詢平均成績大於等於90分的學生的學號和平均成績
select sid as `學號`, avg(score) as `平均成績` from TbSC group by sid having avg(score)>=90;
– 查詢年齡最大的學生的姓名(子查詢)
select stuname from TbStudent where stubirth=(select min(stubirth) from TbStudent);
– 查詢選了兩門以上的課程的學生姓名(子查詢/分組條件/集合運算)
select stuname from TbStudent where stuid in
(select sid from TbSC group by sid having count(sid)>2);
– 查詢選課學生的姓名和平均成績(子查詢和連接查詢)
-- 寫法1:
select stuname, avgscore from TbStudent t1 inner join
(select sid, avg(score) as avgscore from TbSC where score is not null group by sid) t2
on t1.stuid=t2.sid;
-- 寫法2:
select stuname, avgscore from TbStudent t1,
(select sid, avg(score) as avgscore from TbSC where score is not null group by sid) t2
where t1.stuid=t2.sid;
– 查詢學生姓名、所選課程名稱和成績(連接查詢)
-- 寫法1:
select stuname, cosname, score from
TbStudent t1, TbCourse t2, TbSC t3
where t1.stuid=t3.sid and t2.cosid=t3.cid and t3.score is not null;
-- 寫法2:
select stuname, cosname, score from TbStudent t1 inner join TbCourse t2
inner join (select sid, cid, score from TbSC where score is not null) t3
on t1.stuid=t3.sid and t2.cosid=t3.cid;
– 查詢每個學生的姓名和選課數量(左外連接和子查詢)
select stuname as `姓名`, ifnull(coscount, 0) as `選課數` from TbStudent t1
left outer join (select sid, count(sid) as coscount from TbSC group by sid) t2
on t1.stuid=t2.sid;