Allow GROUP BY and HAVING to reference SELECT expressions by ordinal and alias. It is not standard SQL, but MySQL and PostgreSQL allow it.
It would be enabled only by new methods isGroupByOrdinal and isGroupByAlias in SqlConformance.
We might allow alias in the HAVING clause (as described in HIVE-10557) but ordinal does not make sense.
Expressions that are not available before grouping would be illegal; for instance:
We'd also need rules to resolve ambiguous expressions. For instance, in
does deptno refer to e.deptno, d.deptno, or e.empno?