sas - 可以将带有 max 函数的子选择转换为 SAS 数据步吗？

Question

是否可以将下面的代码从 proc sql 转换为 sas datastep？

proc sql;
create table CAL_CHECK as
select t1.DT_REP 
     , t1.BANK_FLAG
     , (select MAX(t2.DT_REP) as LAST_BD_BANK_FLAG from CZ_LOOK.CZ_CALENDAR t2 where t2.DT_REP < t1.DT_REP and t2.BANK_FLAG='Y') as LAST_BD 
from CZ_LOOK.CZ_CALENDAR t1
where dt_rep between &first_day. and &last_day.;
quit;

感谢您的回复

例子：

DT_REP      LAST_BD
01.04.2020  31.03.2020
02.04.2020  01.04.2020
03.04.2020  02.04.2020
04.04.2020  03.04.2020
05.04.2020  03.04.2020
06.04.2020  03.04.2020
07.04.2020  06.04.2020
08.04.2020  07.04.2020

1.4. 是星期三，所以最后一个银行日是 31.3、5.4
。是星期天，所以最后一个银行日是
3.4、6.4。是星期一，所以最后一个银行工作日是 3.4。至

Answer 1

是的。子选择是自相关的子选择。

人们可能会认为 LAG 是合适的，但是，bank_flag 条件使得无法将 LAG 用于手头的任务。

仅在使用其先前状态的值之后保留last_bd和更新其值本质上将根据需要有条件地滞后变量。

例子：

data CZ_CALENDAR;
  input (DT_REP LAST_BD) (ddmmyy10.:) bank_flag: $1. ;
  format dt_rep last_bd yymmdd10.;
datalines;
31.03.2020  .           Y Tue
01.04.2020  31.03.2020  Y Wed
02.04.2020  01.04.2020  Y Thu
03.04.2020  02.04.2020  Y Fri
04.04.2020  03.04.2020  N Sat
05.04.2020  03.04.2020  N Sun
06.04.2020  03.04.2020  Y Mon
07.04.2020  06.04.2020  Y Tue
08.04.2020  07.04.2020  Y Wed
;

%let first_day = '01JAN2020'D;
%let last_day = "&SYSDATE."D;

%put NOTE: &=first_day;
%put NOTE: &=last_day;

proc sql;
  create table CAL_CHECK as
  select
    t1.DT_REP 
    , t1.BANK_FLAG
    , ( select MAX(t2.DT_REP) as LAST_BD_BANK_FLAG 
       from CZ_CALENDAR t2 
       where t2.DT_REP < t1.DT_REP and t2.BANK_FLAG='Y'
      )
      as LAST_BD 
  from
    CZ_CALENDAR t1
  where
    dt_rep between &first_day. and &last_day.;
quit;

proc print data=CAL_CHECK;
  title "SQL";
  format dt_rep last_bd WEEKDATE.;
run;

proc sort data=cz_calendar;
  by dt_rep;

data cal_check2(where=(dt_rep between &first_day. and &last_day.));
  set cz_calendar;

  OUTPUT;

  * save dt_rep from most recent bank_flag day;
  retain last_bd;
  if bank_flag = 'Y' then last_bd = dt_rep;
run;

proc print data=CAL_CHECK2;
  title "DATA step";
  format dt_rep last_bd WEEKDATE.;
run;

输出