1,用户表与关系表：
2，表结构
3，建立约束的表结构
4，创建数据库，创建数据库表，创建约束
create database qqshuju； // 创建数据库
create table baseinfo //创建数据库表baseinfo
（
QQID INT PRIMARY KEY NOT NULL,
nickname VARCHAR(32),
sex INT,
apeint INT,
province VARCHAR(32) ,
cky VARCHAR (32),
`address` VARCHAR(32),
phone INT
）
create table QQUser //创建数据库表 QQUser
（
QQID INT PRIMARY KEY NOT NULL,
nickname VARCHAR(32),
sex INT,
age INT,
province VARCHAR(32) ,
cky VARCHAR (32),
`address` VARCHAR(32),
phone INT
）
create table Relation //创建数据库表 Relation
（
QQID INT PRIMARY KEY NOT NULL,
nickname VARCHAR(32),
sex INT,
apeint INT,
province VARCHAR(32) ,
cky VARCHAR (32),
`address` VARCHAR(32),
phone INT
）
//查看上面的图片创建三个表之间的关系
#在QQUser中创建baseinfo的外键约束
ALTER TABLE `QQUser`
ADD CONSTRAINT FK_QQUser_baseinfo_QQID FOREIGN KEY(QQID)
REFERENCES baseinfo(QQID)
注意：上图中 在QQUser 和 baseinfo表之间有一个线，两头分别指向两个表，其意思是两个表都可用作主键表
#在relation中创建QQUser的外键约束
alter table relation
add constraint fk_relation_qquser_qqid foreign key(qqid)
references qquser(qqid)
alter table relation
add contraint fk_relation_qquser_relationqqid foreign ky（relationQQID）
references qquser(qqid)
#在数据表中添加数据
INSERT INTO `baseinfo`( QQID,nickname, sex, apeint, province,cky,address,phone)
VALUES(8856678,'独行侠',1,38,'北京','海淀区','上地',003),(54789625,'蝴蝶飞飞',1,16,'北京','朝阳区','亚运村',001),
(88662753,'青青草',0,20,'河南省','安阳','汤阴',002)
INSERT INTO QQUser(QQID,`password`,lastlogtime,online,`level`)
VALUES(8856678,'quest0221','2008-02-21 16:28:20.000',1,6),(54789625,'add512#%','2008-02-16 17:01:35.000',2,1),
(88662753,'asmin0219','2008-02-19 21:08:35.000',0,5)
INSERT INTO Relation(id,QQID,relationQQID,relationStatus)
VALUES(1,54789625,88662753,0),(2,88662753,8856678,1),(3,54789625,8856678,0)
5，相关题
（1）：查询数据
#01.查询QQ号码为 54789625 的所有好友信息，包括QQ号码，昵称，年
select RelationQQID as QQ号码,NickName as 昵称,Age as 年龄
from BaseInfo,Relation
where BaseInfo.QQID=Relation.RelationQQID
and Relation.QQID=54789625
and RelationStatus=0 或者1
#02.查询当前在线用户的信息
SELECT NickName,Province
FROM BaseInfo,QQUser
WHERE BaseInfo.QQID=QQUser.QQID AND Online=0
#03.查询北京的、年龄在18至45岁之间的在线用户的信息
SELECT NickName,Province
FROM BaseInfo,QQUser
WHERE BaseInfo.QQID=QQUser.QQID
AND BaseInfo.Province LIKE '%北京%'
AND BaseInfo.Age BETWEEN 18 AND 45 // between 值得是两个数中间值
AND Online=0 //默认0为在线
#04.查询昵称为青青草的用户信息
SELECT NickName,Province,Cky,Address
FROM BaseInfo
WHERE NickName='青青草'
#05.查询QQ号码为54789625的用户的好友中每个省份的总人数，并且总人数按由大到小排 序。
SELECT BaseInfo.Province,COUNT(*) AS 总人数
FROM Relation,BaseInfo
WHERE Relation.RelationQQID=BaseInfo.QQID
AND Relation.RelationStatus=0
AND Relation.QQID=54789625
GROUP BY BaseInfo.Province
ORDER BY 总人数 DESC
#06.查询至少有150天未登录QQ账号的用户信息，包括QQ号码，最后一次登录时间、等级、昵称、年龄，并按时间的降序排列
SELECT
QQUser.QQID,QQUser.lastlogtime,QQUser.Level,BaseInfo.NickName,BaseInfo.Age
FROM BaseInfo,QQUser
WHERE BaseInfo.QQID=QQUser.QQID
AND DATEDIFF(NOW(),lastLogTime)>=150
ORDER BY DATEDIFF(NOW(),lastLogTime) DESC
#07.查询QQ号码为54789625的好友中等级为10级以上的“月亮”级用户信息。
SELECT NickName,Province
FROM QQUser,Relation,BaseInfo
WHERE Relation.RelationQQID=BaseInfo.QQID
AND Relation.QQID=54789625
AND Relation.RelationStatus=0
AND Relation.RelationQQID=QQUser.QQID
AND QQUser.Level>=10
#08.--查询QQ号码为54789625的好友中隐身的用户信息。
SELECT NickName,province
FROM Relation INNER JOIN BaseInfo
ON Relation.RelationQQID=BaseInfo.QQID
AND Relation.QQID=54789625
INNER JOIN QQUser
ON QQUser.QQID=RelationQQID
AND Online=2 //2代表隐身
AND Relation.RelationStatus=0 //0代表好友
#09.--查询好友超过20个的用户信息。
SELECT Nickname,province
FROM BaseInfo WHERE QQID IN
(SELECT QQID
FROM Relation
WHERE RelationStatus=0
GROUP BY QQID
HAVING COUNT(*)>20
)
#10.为了查看信誉度，管理员需要查询被当做黑名单人物次数排名前3的用户
SELECT RelationQQID,COUNT(*) AS 次数
FROM Relation
WHERE RelationStatus=1 //默认1为黑名单
GROUP BY RelationQQID
ORDER BY COUNT(*) DESC
LIMIT 3
（2）：修改数据
#01.假设我的QQ号码为8855678，今天我隐身登录
UPDATE QQUser SET Online=2,LastLogTime=NOW
WHERE QQID=8855678
#02.假设我的QQ号码为8855678，修改我的昵称为“被淹死的鱼”，地址为“解放中路号院123室”
UPDATE BaseInfo SET NickName='被淹死的鱼',Address='解放中路号院室'
WHERE QQID=8855678
#03.假设我的QQ号码为54789625，将我的好友“青青草”拖进黑名单。
UPDATE Relation SET RelationStatus=1
WHERE QQID=54789625 AND RelationQQID=88662753
#04.为了提高QQ用户的聊天积极性，把等级小于6级的用户的等级都提升1个级别。
update QQUser set Level=Level+1
where Level<6
#05.管理员将超过365天没有登录过的QQ锁定（即将等级值设定为-1）。
UPDATE QQUser SET LEVEL=-1
WHERE DATEDIFF(NOW(),lastLogTime)>=365
#06.为了奖励用户，将好友数量超过20的用户等级提升1个级别。
UPDATE QQUser SET LEVEL=LEVEL+1
WHERE QQID IN(
SELECT Relation.QQID FROM Relation
WHERE RelationStatus=0
GROUP BY Relation.QQID
HAVING COUNT(Relation.RelationQQID)>=20)
#07.把QQ号码为54789625的用户的好友“嘟嘟鱼”拖进黑名单中。
UPDATE Relation SET RelationStatus=1
WHERE QQID=54789625 AND RelationQQID=
(SELECT QQID FROM BaseInfo WHERE NickName='青青草')
AND RelationStatus=0
（3）：删除数据
#1.把QQ号码为54789625的用户黑名单中的用户删除。
DELETE FROM Relation WHERE QQID=54789625 AND RelationStatus=1
#2.QQ号码为54789625的用户多次在QQ中发布违法信息，造成了很坏的影响，因此管理员决定将其删除。
DELETE FROM Relation WHERE QQID=54789625 OR RelationQQID=54789625
DELETE FROM BaseInfo WHERE QQID=54789625
DELETE FROM QQUser WHERE QQID=54789625
#3.管理员将超过1000天没有登录过的QQ删除。
DELETE FROM Relation WHERE QQID IN
(
SELECT QQID FROM QQUser
WHERE DATEDIFF(NOW(),LastLogTime)>=1000
)
OR RelationQQID IN //在relation表中无论是在qqid列或这relationqqid列的
( //用户都会被删除
SELECT QQID FROM QQUser
WHERE DATEDIFF(NOW(),LastLogTime)>=1000
)
DELETE FROM BaseInfo WHERE QQID IN
(
SELECT QQID FROM QQUser
WHERE DATEDIFF(NOW(),LastLogTime)>=1000
)
DELETE FROM QQUser
WHERE DATEDIFF(NOW(),LastLogTime)>=1000