QQ数据库管理
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1,数据库关系图
##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
辅助blog
mysql 获得当前日期时间 函数
获得当前日期+时间(date + time)函数:now()
mysql> select now();
+---------------------+| now() |+---------------------+| 2008-08-08 22:20:46 |+---------------------+
获得当前日期+时间(date + time)函数:sysdate()
sysdate() 日期时间函数跟 now() 类似,不同之处在于:now() 在执行开始时值就得到了, sysdate() 在函数执行时动态得到值。看下面的例子就明白了:
mysql> select now(), sleep(3), now();
+---------------------+----------+---------------------+| now() | sleep(3) | now() |+---------------------+----------+---------------------+| 2008-08-08 22:28:21 | 0 | 2008-08-08 22:28:21 |+---------------------+----------+---------------------+
sysdate() 日期时间函数,一般情况下很少用到。
MySQL 获得当前时间戳函数:current_timestamp, current_timestamp()
mysql> select current_timestamp, current_timestamp();
+---------------------+---------------------+| current_timestamp | current_timestamp() |+---------------------+---------------------+| 2008-08-09 23:22:24 | 2008-08-09 23:22:24 |+---------------------+---------------------+
MySQL 日期转换函数、时间转换函数
MySQL Date/Time to Str(日期/时间转换为字符串)函数:date_format(date,format), time_format(time,format)
mysql> select date_format(\'2008-08-08 22:23:01\', \'%Y%m%d%H%i%s\');
+----------------------------------------------------+| date_format(\'2008-08-08 22:23:01\', \'%Y%m%d%H%i%s\') |+----------------------------------------------------+| 20080808222301 |+----------------------------------------------------+
MySQL 日期、时间转换函数:date_format(date,format), time_format(time,format) 能够把一个日期/时间转换成各种各样的字符串格式。它是 str_to_date(str,format) 函数的 一个逆转换。
MySQL Str to Date (字符串转换为日期)函数:str_to_date(str, format)
select str_to_date(\'08/09/2008\', \'%m/%d/%Y\'); -- 2008-08-09select str_to_date(\'08/09/08\' , \'%m/%d/%y\'); -- 2008-08-09select str_to_date(\'08.09.2008\', \'%m.%d.%Y\'); -- 2008-08-09select str_to_date(\'08:09:30\', \'%h:%i:%s\'); -- 08:09:30select str_to_date(\'08.09.2008 08:09:30\', \'%m.%d.%Y %h:%i:%s\'); -- 2008-08-09 08:09:30
可以看到,str_to_date(str,format) 转换函数,可以把一些杂乱无章的字符串转换为日期格式。另外,它也可以转换为时间。“format” 可以参看 MySQL 手册。
MySQL (日期、天数)转换函数:to_days(date), from_days(days)
select to_days(\'0000-00-00\'); -- 0select to_days(\'2008-08-08\'); -- 733627
MySQL (时间、秒)转换函数:time_to_sec(time), sec_to_time(seconds)
select time_to_sec(\'01:00:05\'); -- 3605select sec_to_time(3605); -- \'01:00:05\'
MySQL 拼凑日期、时间函数:makdedate(year,dayofyear), maketime(hour,minute,second)
select makedate(2001,31); -- \'2001-01-31\'select makedate(2001,32); -- \'2001-02-01\'select maketime(12,15,30); -- \'12:15:30\'
MySQL (Unix 时间戳、日期)转换函数
unix_timestamp(),
unix_timestamp(date),
from_unixtime(unix_timestamp),
from_unixtime(unix_timestamp,format)
下面是示例:
select unix_timestamp(); -- 1218290027select unix_timestamp(\'2008-08-08\'); -- 1218124800select unix_timestamp(\'2008-08-08 12:30:00\'); -- 1218169800
select from_unixtime(1218290027); -- \'2008-08-09 21:53:47\'select from_unixtime(1218124800); -- \'2008-08-08 00:00:00\'select from_unixtime(1218169800); -- \'2008-08-08 12:30:00\'
select from_unixtime(1218169800, \'%Y %D %M %h:%i:%s %x\'); -- \'2008 8th August 12:30:00 2008\'
MySQL 日期时间计算函数
MySQL 为日期增加一个时间间隔:date_add()
set @dt = now();
select date_add(@dt, interval 1 day); -- add 1 dayselect date_add(@dt, interval 1 hour); -- add 1 hourselect date_add(@dt, interval 1 minute); -- ...select date_add(@dt, interval 1 second);select date_add(@dt, interval 1 microsecond);select date_add(@dt, interval 1 week);select date_add(@dt, interval 1 month);select date_add(@dt, interval 1 quarter);select date_add(@dt, interval 1 year);
select date_add(@dt, interval -1 day); -- sub 1 day
MySQL adddate(), addtime()函数,可以用 date_add() 来替代。下面是 date_add() 实现 addtime() 功能示例:
mysql> set @dt = \'2008-08-09 12:12:33\';
mysql>
mysql> select date_add(@dt, interval \'01:15:30\' hour_second);
+------------------------------------------------+| date_add(@dt, interval \'01:15:30\' hour_second) |+------------------------------------------------+| 2008-08-09 13:28:03 |+------------------------------------------------+
mysql> select date_add(@dt, interval \'1 01:15:30\' day_second);
+-------------------------------------------------+| date_add(@dt, interval \'1 01:15:30\' day_second) |+-------------------------------------------------+| 2008-08-10 13:28:03 |+-------------------------------------------------+
MySQL 为日期减去一个时间间隔:date_sub()
mysql> select date_sub(\'1998-01-01 00:00:00\', interval \'1 1:1:1\' day_second);
+----------------------------------------------------------------+| date_sub(\'1998-01-01 00:00:00\', interval \'1 1:1:1\' day_second) |+----------------------------------------------------------------+| 1997-12-30 22:58:59 |+----------------------------------------------------------------+
MySQL date_sub() 日期时间函数 和 date_add() 用法一致,不再赘述。
MySQL 日期、时间相减函数:datediff(date1,date2), timediff(time1,time2)
MySQL datediff(date1,date2):两个日期相减 date1 - date2,返回天数。select datediff(\'2008-08-08\', \'2008-08-01\'); -- 7select datediff(\'2008-08-01\', \'2008-08-08\'); -- -7
MySQL timediff(time1,time2):两个日期相减 time1 - time2,返回 time 差值。
select timediff(\'2008-08-08 08:08:08\', \'2008-08-08 00:00:00\'); -- 08:08:08select timediff(\'08:08:08\', \'00:00:00\'); -- 08:08:08
注意:timediff(time1,time2) 函数的两个参数类型必须相同。
MySQL 时间戳(timestamp)转换、增、减函数:
timestamp(date) -- date to timestamptimestamp(dt,time) -- dt + time
timestampadd(unit,interval,datetime_expr) --timestampdiff(unit,datetime_expr1,datetime_expr2) --
请看示例部分:
select timestamp(\'2008-08-08\'); -- 2008-08-08 00:00:00select timestamp(\'2008-08-08 08:00:00\', \'01:01:01\'); -- 2008-08-08 09:01:01select timestamp(\'2008-08-08 08:00:00\', \'10 01:01:01\'); -- 2008-08-18 09:01:01
select timestampadd(day, 1, \'2008-08-08 08:00:00\'); -- 2008-08-09 08:00:00select date_add(\'2008-08-08 08:00:00\', interval 1 day); -- 2008-08-09 08:00:00
MySQL timestampadd() 函数类似于 date_add()。select timestampdiff(year,\'2002-05-01\',\'2001-01-01\'); -- -1select timestampdiff(day ,\'2002-05-01\',\'2001-01-01\'); -- -485select timestampdiff(hour,\'2008-08-08 12:00:00\',\'2008-08-08 00:00:00\'); -- -12
select datediff(\'2008-08-08 12:00:00\', \'2008-08-01 00:00:00\'); -- 7
MySQL timestampdiff() 函数就比 datediff() 功能强多了,datediff() 只能计算两个日期(date)之间相差的天数。
MySQL 时区(timezone)转换函数
convert_tz(dt,from_tz,to_tz)
select convert_tz(\'2008-08-08 12:00:00\', \'+08:00\', \'+00:00\'); -- 2008-08-08 04:00:00
时区转换也可以通过 date_add, date_sub, timestampadd 来实现。
select date_add(\'2008-08-08 12:00:00\', interval -8 hour); -- 2008-08-08 04:00:00select date_sub(\'2008-08-08 12:00:00\', interval 8 hour); -- 2008-08-08 04:00:00select timestampadd(hour, -8, \'2008-08-08 12:00:00\'); -- 2008-08-08 04:00:00
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