表结构
##用例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，年龄
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
AND Online=0
#04.查询昵称为青青草的用户信息
SELECT NickName,Province,City,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
GROUP BY RelationQQID
ORDER BY COUNT(*) DESC
LIMIT 3
##用例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='嘟嘟鱼')
AND RelationStatus=0
##用例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
(
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