Como ter uma ordem de classificação personalizada para uma consulta de união no Postgres
Com uma consulta como esta (simplificada para maior clareza):
SELECT 'East' AS name, *
FROM events
WHERE event_timestamp BETWEEN '2015-06-14 06:15:00' AND '2015-06-21 06:15:00'
UNION
SELECT 'West' AS name, *
FROM events
WHERE event_timestamp BETWEEN '2015-06-14 06:15:00' AND '2015-06-21 06:15:00'
UNION
SELECT 'Both' AS name, *
FROM events
WHERE event_timestamp BETWEEN '2015-06-14 06:15:00' AND '2015-06-21 06:15:00'
Eu quero personalizar a ordem das linhas resultantes. Algo como:
ORDER BY name='East', name='West', name='Both'
Ou
ORDER BY
CASE
WHEN name='East' THEN 1
WHEN name='West' THEN 2
WHEN name='Both' THEN 3
ELSE 4
END;
No entanto, o Postgres reclama com:
ERROR: invalid UNION/INTERSECT/EXCEPT ORDER BY clause
DETAIL: Only result column names can be used, not expressions or functions.
HINT: Add the expression/function to every SELECT, or move the UNION into a FROM clause.
Eu tenho alguma alternativa?