SQL 宏

Given the SAS data set SASUSER.HIGHWAY:

Steering    Seatbelt  Speed  Status   Count
 -------- -------- ----- ------- -----
 absent       No       0-29  serious    31
 absent       No       0-29     not    1419
 absent       No      30-49  serious   191
 absent        no      30-49  not      2004
 absent        no        50+  serious   216

The following SAS program is submitted:

 proc sql noprint;
 select distinct Speed [_insert_SQL_clause_]
 from SASUSER.HIGHWAY
 ;
 quit;
 title1 “Speed values represented are: &GROUPS”;
 proc print data=SASUSER.HIGHWAY;
 run;

Which SQL clause stores the text 0-29,30-49,50+ in the macro variable GROUPS?
A. into &GROUPS
B. into :GROUPS
C. into :GROUPS separated by ‘,’
D. into &GROUPS separated by ‘,
解析 B是把该列第一个变量付给宏变量group
C是把一整列付给宏变量group 用 ’ , '分隔