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sqlteradata-sql-assistant

Joining tables selecting values that exist only in one table

I have two tables

A
ID age  
1   24
2   25
45  22

B 
Name school Surname
34  school1  141
1   school2  152

I want to select Surname from B only for those Names that are not in A. ID and name have the same meaning in the two tables, but different name. I wrote

Select distinct bb.Surname
From B as bb 
Left outer join A as aa 
On bb.Name=aa.ID

But the number of rows is the same as an inner join between the two tables. I have approximately 100000 rows, so I cannot check manually. Do you spot failures in my approach?

The answer provided is not solving the issue as I am getting the same values as an inner join, so something is clearly wrong.

Solution 
  •    select b.surname
   from tableb as b
   left join tablea as a on b.name=a.id
   where a.id is null