【sas sql proc】inner join or outer join

proc sql;
    title 'table 1+11';
    select * from mysas.ifthen1,mysas.ifthen11;
quit;

proc sql;
    title 'table 1';
    select * from mysas.ifthen1;
    
    title 'table11';
    select * from mysas.ifthen11;
quit;

第一段显示的是两表联合的笛卡尔积结果。

第二段仅是分别显示两表。

proc sql;
    title 'table1 inner jion table11';
    select a.gtone as g from mysas.ifthen1 a,mysas.ifthen11 b
    where a.gtone=b.gtone;
quit;
proc sql;
    title 'table1 inner jion table11';
    select a.gtone  'g' from mysas.ifthen1 a,mysas.ifthen11 b
    where a.gtone=b.gtone;
quit;

行的别名，两种方式一种是标签，另一种是另起名。

 from where 和inner join +on的作用一致 inner join +on是为了和left/right join on 相统一。

proc sql;
    title 'self join';
    select a.gtone,b.shen
    from mysas.ifthen1 a,mysas.ifthen1 b
    where a.date=b.date;
quit;

用别名可以实现自身与自身的查询。