sas合并数据集，大家快帮忙 ，我快哭了

proc sql;
    select a.* ,b.* ,c.*,d.*,e.*
   from a join b join c join d join e
   using(x);quit;

proc sql;
    select a.* ,b.* ,c.*,d.*,e.*
   from a full join b full join c full join d full join e
   using(x);
quit;
不知道用不用加full