ıf komutunu ve değişken nasıl kullanılır

[harunkomus]

CASE KOMUTUNU KULLANABİLİYOTUM AMA İF KOMUTNU NE YAPSAM
HATA VERİYOR

ÖRNEK AŞAĞIDAKİ KOMUTLARI IF KOMUTU İLE NASIL KULLANABİLRİM
---------------------------------------------------------------------------------------------------------------
OCAK = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=1
then SUM(LG_029_01_STLINE.AMOUNT)
END,
SUBAT = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=2
then SUM(LG_029_01_STLINE.AMOUNT)
END,
MART = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=3
then SUM(LG_029_01_STLINE.AMOUNT)
END,
NİSAN = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=4
then SUM(LG_029_01_STLINE.AMOUNT)
END,
MAYIS = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=5
then SUM(LG_029_01_STLINE.AMOUNT)
END,
HAZİRAN = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=6
then SUM(LG_029_01_STLINE.AMOUNT)
END,
TEMMUZ = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=7
then SUM(LG_029_01_STLINE.AMOUNT)
END,
AGUSTOS= CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=8
then SUM(LG_029_01_STLINE.AMOUNT)
END,
EYLUL = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=9
then SUM(LG_029_01_STLINE.AMOUNT)
END,
EKİM = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=10
then SUM(LG_029_01_STLINE.AMOUNT)
END,
KASIM = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=11
then SUM(LG_029_01_STLINE.AMOUNT)
END,
ARALIK = CASE when DATEPART(mm,LG_029_01_STLINE.DATE_)=12
then SUM(LG_029_01_STLINE.AMOUNT)
END



DEĞİŞKEN ATAMA YAPMAK
---------------------------------------------
SELECET ANA TABLO....
BORÇ: SELECT SUM(TUTAR) .... GRUB BY... ,
ALACAK: SELECT SUM(TUTAR)..... GRUB BY.... ,
DEĞİKEN3= DEĞİŞKEN1+DEĞİKEN2

BURADA DEĞİŞKEN OLMUYOR HATA VERİYOR

HER HESAP HAREKETİNE HEP SELECT DEMEK OLUYOR