查询本月信息：
Select * FROM T_Users Where datediff(month,RegisterTime,getdate())=0

昨天的信息：
SELECT * FROM T_Users where LastLoginTime>DATEADD(DAY,-2,GETDATE()) AND LastLoginTime<GETDATE()

SELECT SUM([DetailMoney]) FROM [dbo].[T_BuyDetails] INNER JOIN [dbo].[T_Users] ON [CommenderID]=[UserID]
WHERE datediff(month,[DateTime],getdate())=0

--本月

SELECT SUM([DetailMoney]) FROM [dbo].[T_BuyDetails]
INNER JOIN [dbo].[T_Users] ON [CommenderID]=[UserID]
WHERE CONVERT( char(10),[DateTime],120)>CONVERT(char(10),DATEADD(DAY,-2,GETDATE()),120) AND CONVERT( char(10),[DateTime],120)<CONVERT( char(10),GETDATE(),120)

--昨日

SELECT SUM([DetailMoney]) FROM [dbo].[T_BuyDetails]
WHERE CONVERT( char(10),[DateTime],120)=CONVERT( char(10),GETDATE(),120)

--今日

SELECT SUM([DetailMoney]) FROM [dbo].[T_BuyDetails]

--总消费