SAS 递归连接

Question

我有一个大的连接表，并希望扩展该表以包含递归连接。

我的数据看起来像这样--

data city_list;  

input from_city $ to_city $;
datalines;  
PORTLAND SEATTLE
SEATTLE BOISE
BOISE PORTLAND
PORTLAND HELENA
NYC ORLANDO
ORLANDO MIAMI
;
run;

我想扩展数据集以包括中途停留，所以它最终看起来像这样。我不关心我是否同时拥有“PORTLAND/SEATTLE”和“SEATTLE/PORTLAND”记录——之后我可以根据需要处理这些记录。

BOISE   HELENA
BOISE   PORTLAND
BOISE   SEATTLE
NYC MIAMI
NYC ORLANDO
ORLANDO MIAMI
PORTLAND    HELENA
PORTLAND    SEATTLE
SEATTLE HELENA

我尝试使用以下宏，但是当递归级别过多时遇到了性能问题。我相信最好的选择是哈希表，但我不确定如何编写这种精确的场景。

data city_list;  

input from_city $ to_city $;
datalines;  
PORTLAND SEATTLE
SEATTLE BOISE
BOISE PORTLAND
PORTLAND HELENA
NYC ORLANDO
ORLANDO MIAMI
;
run;

%macro RecurJoin(
baseTbl,
destTbl,
baseKey,
compKey
);

Proc SQL;
Create Table WORK.RECUR_JOIN_TBL as
SELECT distinct Base.&baseKey, Connect.&compkey
  FROM &baseTbl AS Base
       INNER JOIN &baseTbl AS Connect
          ON (Base.&compkey = Connect.&baseKey)
       LEFT JOIN &baseTbl AS Subbase
          ON (Base.&baseKey = Subbase.&baseKey) AND
             (Connect.&compkey = Subbase.&compkey)
 WHERE Subbase.&baseKey IS NULL;
quit;

  proc sql noprint;
    select count(1) into :connectCnt from RECUR_JOIN_TBL;
  quit;

Data &destTbl;
  set &baseTbl
      RECUR_JOIN_TBL;
run;

    Proc DataSets nolist;
        Delete RECUR_JOIN_TBL;
    Quit;

%if &connectCnt > 0 %then %do;
    %RecurJoin(
    baseTbl=&destTbl,
    destTbl=&destTbl,
    baseKey=&baseKey,
    compKey=&compKey
    );
%end;

%mend;

%RecurJoin(
baseTbl=city_list,
destTbl=FNL_CITY_LIST,
baseKey=from_city,
compKey=to_city
);

Proc Sort data=WORK.FNL_CITY_LIST (where=(NOT(from_city=to_city)));
  by from_city to_city;
run;

Answer 1

如果内存允许，您可以使用我在this answer 中提出的基于哈希的方法来识别数据集中连接的城市组。然后，您只需为同一组中的每一对城市生成一行，这可以通过proc sql 中的笛卡尔连接轻松完成。