SAS ADV 63题之43

Item 43 of 63 Mark item for review 

  Given the SAS data set WORK.ONE:      

      Rep         Cost 

      -----       ---- 

      SMITH        200 

      SMITH        400 

      JONES        100 

      SMITH        600 

      JONES        100 

  The following SAS program is submitted:

  proc sql;  

     select  

        Rep, 

        avg(Cost) as Average   

     from WORK.ONE     

     [either__insert_SQL_where_clause_]     

     group by Rep

     [_or_  _insert_SQL_having_clause_]

     ;

  quit;

  The following output is desired:       

      Rep        Average

      -----      -------

      SMITH          400

  Which SQL clause completes the program and generates the desired output?     

     A.

 where calculated Average > (select avg(Cost) from WORK.ONE)

     B.

 having Average   > (select avg(Cost) from WORK.ONE)

     C.

 having avg(Cost) < (select avg(Cost) from WORK.ONE)

     D.

 where avg(Cost)  > (select avg(Cost) from WORK.ONE)

这道题主要考察关于having和where的知识。 

having的用法： 和group搭配使用。group用来把data分成subset，having用来选择符合条件的subset. 所以having何以和summary function一起用，比如sum, avg之类的

where的用法： where只能用之与单独的列，不能和summary function一起用

所以答案应该是：B