在以表别名为前缀的字段上使用“计算”​​功能-SAS SQL

Question

I am trying to get the following Proc SQL step to work in SAS 9.2, but it is falling over as it doesn't seem to like my using a table alias to define a field that is in both tables during a merge:

proc sql;
create table test1 as 
select 
a.var1,
b.var2 * -1 as var2,
b.var3,
calculated b.var1 * a.var2 as var4
from table1
left join
table2
on a.var5 = b.var5;
quit;

Without the table alias between the 'Calculated' command and the field name, this code would execute without issue. Does anyone know the syntax I am looking for to get around this?

If I don't use the calculated command the SQL step does not recognise that the calculation used when defining the field 'var1'.

Thanks

Answer 1

CALCULATED tells it to refer to a column that exists in the output (in the select), not in an input dataset, so the table alias doesn't make any sense. CALCULATED var2 is all you need.

proc sql;
  create table test1 as 
   select 
     a.var1,
     b.var2 * -1 as var2,
     b.var3,
     calculated var2 * a.var1 as var4
   from table1
    left join table2
    on a.id=b.id;
quit;

That would be okay, as long as it didn't decide b.var2 * -1 was just a rename.

Answer 2

You are attempting to create a table that has two columns with the same name ( var1 ). I'm not surprised that proc sql is complaining. Try giving them different names:

proc sql;
create table test1 as 
    select a.var1 as a_var1,
           b.var1 * -1 as b_var1,
           b.var2,
           calculated b_var1 * a.var1 as var3
    from table1 left join
         table2
         on a.var4 = b.var4;
quit;