update tb set a=1+1,b=2+2 from tb2 tb22 join tb3 tb33 on tb2.ff = tb3.ff
go
update tb set a=1+1,b=2+2
go
update tb set a=1+1,b=2+2 from tb2 tb22 join tb3 tb33 on tb2.ff = tb3.ff
go