两个数据集之间的日期比较

Question

假设有两个数据集：

data DB1;
  input ID :$20.Reference_date :date9. Discharge :date9.;
  format Reference_date Discharge date9.;
cards;
0001  14JUN2017  19JUN2017 
0002  12MAR2016  17MAR2016  
0003  01MAY2016  05MAY2016  
0004  19MAR2017  22MAR2017
0005  10MAR2017  22MAR2017 
0007  10OCT2015  14OCT2015  
;


data DB2;
  input ID :$20.Discharge_new :date9.;
  format Discharge_new date9.;
cards;
0001 21JUN2017
0002 13MAR2016
0003 04MAY2016
0004 19MAR2017
0005 22MAR2017
0006 27JUN2022
0007 18OCT2015
;

有没有办法检查对于每个ID，来自DB2的discharge_new是否在Reference_date-Discharge的区间内（>=; <=) of DB1? If yes add a Flag = 1 (otherwise Flag = 0) to DB2 to get DB3. Note that there are some IDs in DB2 not present in DB1 that should remain missing. I don't know how to deal with dates comparison from two different datasets.

提前谢谢您。

所需输出：

data DB3;
  input ID :$20.Discharge_new :date9. Flag :$20.;
  format Discharge_new date9.;
cards;
0001 21JUN2017   0
0002 13MAR2016   1
0003 04MAY2016   1
0004 19MAR2017   1
0005 22MAR2017   1
0006 27JUN2022   .
0007 18OCT2015   0
;

Answer 1

这假设您的数据按 ID 排序并且不存在重复的 ID（这两者在您的示例数据中都是正确的）。

在合并时使用

(in =  )

数据集选项来创建检查，以确保该行存在于相关数据集中。

data db3;
    merge db1 (in = indb1) db2 (in = indb2);
    by id;
    * only keep rows from db2;
    if indb2; 
    * only assign a flag of 1 or 0 if there is a match in db1
    if indb1 then do;
        if discharge_new <= reference_date <= discharge then flag = 1;
        else flag = 0;
    end;
    keep id discharge_new flag;
run;