ERROR 1054 resolving a qualified, unprojected GROUP BY column when another group key has the same name

Description

MariaDB Server 12.3.2 rejects a qualified column reference in HAVING even though the column is present in GROUP BY. The reduced query groups two derived tables by their respective `a` columns, and projects only a constant. Both qualified group keys are valid and unambiguous, but `HAVING x.a > 0` raises ERROR 1054.

Projecting `x.a`, or giving the other table's group key a different name, makes the query succeed. A correlated subquery inside HAVING encounters the same problem, reported as an unknown column in WHERE.

How to repeat

SELECT 1 AS result

FROM (SELECT 1 AS a) AS x

CROSS JOIN (SELECT 2 AS a) AS y

GROUP BY x.a, y.a

HAVING x.a > 0;

Actual result

ERROR 1054 (42S22): Unknown column 'x.a' in 'HAVING'