Query To View With Many Columns

Hi All,
I have a simple question. If I have a view that query from joined multiple tables and return a lot of columns (more than 100). If I run a simple query just return several columns (e.g. 4-5 columns), will SQL Server query all columns first from all joined table? or can SQL Server query only necessary column from related table?


Does anyone have idea how to join table that can reflect both left and right join?
Table A Table B
Column1 Column2 Column3 Column4 Column1 Column2 Column 3 Column5
A Jan 5 xxx A Jan 1 yyy
B Feb 3 C Mar 4
B Mar 4 C Apr 3
C Apr 2 D May 2
E Mar 1

Result Table
Column1 Column2 Column3 Column4 Column 5
A Jan 6 (= 5+1) xxx yyyy
B Feb 3
B Mar 4
C Mar 4
C Apr 5 (= 2+3)
D May 2
E Mar 1

So the result table is a join on column1 and column2 (both are primary key), with column3 is a sum aggregate. Table A has additional column4 and Table B has additional column5, so quite difficult to union (In fact, there are a lot of column differences between table).

Thanks for the help.