因不知道你想要 的结果是什么，所以给出了三种结果。

三百个数据集，太复杂了。

简单一点， 举个例子，比如十个数据集，满足什么条件，如何挑选，结果是什么。

也许有人帮忙。

谢谢，受你用SQL的启发，我解决这个问题了。
%MACRO repeatmake;


data earnrate_count;
set stock.earnstatics;
if buydate>=19203 and buydate<selldate;
run;

data all_earnstatics(keep=num buydate selldate earnrate);
set earnrate_count;
run;

proc sort data=earnrate_count nodupkey;
by buydate;
run;

proc sort data=all_earnstatics nodupkey;
by num buydate;
run;


data _null_;
set earnrate_count;
call symput ('number_date',_n_);
run;

sasfile all_earnstatics load;

%do date_num=1 %to &number_date;

data temp_date;
set earnrate_count;
if _n_=&date_num;
run;

data _null_;
set temp_date;
call symput ('temp_buydate',buydate);
run;

data stockhot.temp&date_num;
set all_earnstatics;
if buydate=&temp_buydate;
run;

data stockhot.temp&date_num(keep=buydate&date_num selldate&date_num earnrate&date_num);
set stockhot.temp&date_num;
rename buydate=buydate&date_num;
rename selldate=selldate&date_num;
rename earnrate=earnrate&date_num;
run;


%end;

sasfile all_earnstatics close;


data stock.buyways;
delete;
run;

%do date_num=1 %to &number_date;

%if &date_num=1 %then %do;

data buyways;
set stockhot.temp&date_num;
run;

data stock.buyways;
set buyways;
run;

%end;
%else %do;

data _null_;
call symput ('former_num',trim(left(&date_num-1)));
run;

data temp_b;
set stockhot.temp&date_num;
run;



  proc sql;
   create table temp_buyways as
   select *
   from buyways, temp_b
quit;



data buyways;
set temp_buyways;
run;

data stock.buyways;
set temp_buyways;
run;


%end;
%end;



%do date_num=1 %to &number_date;

data _null_;
call symput ('former_num',trim(left(&date_num-1)));
run;


data stock.buyways;
set stock.buyways;
if selldate&former_num>buydate&date_num then earnrate&date_num=0;
if selldate&former_num>buydate&date_num then selldate&date_num=selldate&former_num;
run;

%end;


data stock.buyways;
set stock.buyways;
earnrate_all=1;
run;

%do date_num=1 %to &number_date;

data stock.buyways;
set stock.buyways;
earnrate_all=earnrate_all+earnrate&date_num*earnrate_all;
run;

%end;





%mend repeatmake;

%repeatmake;

结合SQL和宏使用。谢谢啊！