Github user dongjoon-hyun commented on the pull request:
https://github.com/apache/tajo/pull/543#issuecomment-94321615
Oh. Thank you, @jihoonson .Now, I understand more about your concern and
what causes disagreement.
First, this issue is related ORDER BY SQL name resolution rules rather than
SQL name resolution. The scope is totally different. I think we need to focus
what is the meaning of ORDER BY clause. In that sense, please note that *"it
can optionally be sorted"*. ORDER BY is defined on the SELECT clause. If you
ask 'Why this rule focuses on only order-by clause?', the reason is ORDER BY
clause is different from the others.
Second, let me answer your remaining concerns.
* Why does the same rule can be applied to group-by clauses or any other
clauses? --> We can not. As you know, the other clause affect SELECT clause;
e.g. GROUP BY clause will generate aggregate functions on SELECT clause.
* What happens if the select and order-by clauses involve two or more
columns? --> Each column among them should be need to be resolved
independently. In case of multiple matching, we should print out 'Ambiguous
Column Name Error' again. I think it is logical. If you agree with this, I will
add more codes and testcases for this.
Thank you for you kind guide, again, @jihoonson .
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