SQL get monthly/weekly data sum?

Question

I get Daily sum of data with these lines?

SELECT convert(varchar, okuma_tarihi, 102) as Gunler,SUM(toplam_kullanim_T1) as TotalUsageValue,'T1' as UsageType FROM TblSayacOkumalari
GROUP BY convert(varchar, okuma_tarihi, 102)
UNION ALL
SELECT convert(varchar, okuma_tarihi, 102) as Gunler,SUM(toplam_kullanim_T2) as TotalUsageValue,'T2' as UsageType FROM TblSayacOkumalari 
GROUP BY convert(varchar, okuma_tarihi, 102)
UNION ALL
SELECT convert(varchar, okuma_tarihi, 102) as Gunler,SUM(toplam_kullanim_T3) as TotalUsageValue,'T3' as UsageType FROM TblSayacOkumalari
GROUP BY convert(varchar, okuma_tarihi, 102)

How Can I get SUM of data weekly or mounthly? Is there any turorial about this topic or code example? When I write MONTH(DATE) instead of convert(varchar, okuma_tarihi, 102) It shows , for example all sum of data in that month. (2010 june value + 2011 june value). I dont want this. I use MSSQL Server 2008.

Thanks.

Solution

Use

GROUP BY YEAR(<date_column_name>),MONTH(<date_column_name>) --for months

Or

GROUP BY YEAR(<date_column_name>),DATEPART(wk,<date_column_name>) --for weeks