statement between inner and outer do loop in nested do loop

[SAS_inquisitive]

How does the statement between inner and outer do loop execute? Under which conditions is it necessary to put statement  between inner and outer loop?

data test1;
	put _all_;

	do i= 1 to 2;
		a=10;

		do j=1 to 3;
			put _all_;
			output;
		end;
	end;
run;

data test2;
	put _all_;

	do i= 1 to 2;
		do j=1 to 3;
			a=10;
			put _all_;
			output;
		end;
	end;
run;

[ballardw · Accepted solution]

The difference would be when to you want to change a value or perform an action.

If you want to execute it before the J loop, then the first. If you want to change the value or do the action each time then inside the inner loop. Your example doesn't really show much difference. But look at this difference:

data test1;
	put _all_;
        a=0;
	do i= 1 to 2;
		a=  a + 1;

		do j=1 to 3;
			put _all_;
			output;
		end;
	end;
run;

data test2;
	put _all_;
        a=0;
	do i= 1 to 2;
		do j=1 to 3;
			a= a + 1;
			put _all_;
			output;
		end;
	end;
run;

You may want to do something only after the the inner loop has completed, in which case it would go after the inner loop.