Case - When - Update - Insert Into - End

Hi guys,

My first question is, is it possible like this?

case
when a=b then
update table1
set columnA = convert(datetime,columnB,113)
from table2
where a=b
insert into table1 (columnames)
select (few columns, and few defined value)
from table2
where a=b
else
insert into table1 (columnames)
select (few columns)
from table2
where a=b
end

from there u can know im a newbie n know nothing bout sql :D

Thanks in advance guys!