规定临时变量选项（NOBS=）

DATA A;
	SET SASHELP.CLASS;
	OBS=_N_;
RUN;

DATA B;
	/* 当N=1时加3并赋值给LAST */
	DO N=1 TO LAST BY 3;
	/* 显示第N行，下一条为LAST行 */
	SET A POINT=N NOBS=LAST;
	OUTPUT;
	END;
	STOP;
RUN;

PROC PRINT; RUN;