topic Re: Is there a difference between LEFT Outer JOIN and RIGHT Outer JOIN? in New SAS User

Is there a difference between LEFT Outer JOIN and RIGHT Outer JOIN?

cosmid — Sun, 10 Dec 2023 21:40:04 GMT

Thanks

Re: Is there a difference between LEFT Outer JOIN and RIGHT Outer JOIN?

Patrick — Sun, 10 Dec 2023 22:10:25 GMT

Keep all rows from the left side as opposed to keep all rows from the right side. But if you have a left join formulated and then switch to a right join and also switch your source tables accordingly then the result will be the same.

Re: Is there a difference between LEFT Outer JOIN and RIGHT Outer JOIN?

cosmid — Sun, 10 Dec 2023 22:11:28 GMT

So they are essentially the same?

Re: Is there a difference between LEFT Outer JOIN and RIGHT Outer JOIN?

Patrick — Mon, 11 Dec 2023 02:16:49 GMT

Depending on how you look at it - yes.

data have1;
  var1=1;
  do id=1,3,6;
    output;
  end;
run;
data have2;
  var2=1;
  do id=1 to 5;
    output;
  end;
run;

proc sql;
  select t1.id, t1.var1, t2.var2
  from have1 t1 left join have2 t2
    on t1.id=t2.id
  ;
quit;

proc sql;
  select t1.id, t1.var1, t2.var2
  from have2 t2 right join have1 t1
    on t1.id=t2.id
  ;
quit;