update tble
set t1=值,t2=值
from not t1 is null and not t2 is null
update tableA
set column1=case when column2 is not null then column2 else column1 end,
column2=
case when column1 is not null then column1 else column2 end
where column1 is not null or column2 is not null
update tb
set col1=col2
where col1 is not null and col2 is not null