关于 数据库查询命令

来源：百度知道 编辑：UC知道 时间：2024/07/07 11:14:13
sql="select T1.UserName,UserEmail,T2.HomePage,Sum(1) AS TiaoShu,Sum(IIF(DateDiff('d',T3.UpdateTime,T1.ReplyTime)<3,1,0)) AS TiaoShu2ri from (ArticleComment AS T1 Inner Join Article AS T3 On T1.ArticleId=T3.ArticleId) Inner Join Dv_User AS T2 On T1.UserName=T2.UserName Group By T1.UserName,UserEmail,T2.HomePage Order by Sum(1) DESC"

谁能给我个中文解释和翻译？越详细越好...百分求解！
请教哪有这方面知识的网站吗!或资料!?关于数据库筛选统计的..

1.select * FROM A where 列名 <>0
--<>标示不等于
2.--NOT in
select * FROM A where 列名 NOT in(0)
--这样是用索引的 不用担心。
3.--子查询  WHERE
SELECT * FROM A  WHERE A NOT IN (SELECT 列名FROM A WHERE A ='1')

sql="select T1.UserName,UserEmail,T2.HomePage,Sum(1) AS TiaoShu,Sum(IIF(DateDiff('d',T3.UpdateTime,T1.ReplyTime)<3,1,0)) AS TiaoShu2ri

选择：t1表的username，useremail，T2表的homepage，所有条数汇总用并且在提示中使用Tiaoshu这个名字，汇总T3的updatetime与T1表中replytime时间差别小于3天的条数并且用Tiaoshu2ri表示

from (ArticleComment AS T1 Inner Join Article AS T3 On T1.ArticleId=T3.ArticleId) Inner Join Dv_User AS T2 On T1.UserName=T2.UserName

从T1 和T3 根据T1.ArticleId=T3.ArticleId的调节进行内连接后，与T2表在此根据T1.UserName=T2.UserName的条件进行内连接的结果中选择
其中T1是ArticleComment表的别名，T2是Dv_User表的别名，T3是Article表的别名

Group By T1.UserName,UserEmail,T2.HomePage

结果按照T1的username ，useremail，T2的homepage进行分组

Order by Sum(1)