使用这样的查询（为清楚起见，已简化）：
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'
我想自定义结果行的顺序。就像是：
ORDER BY name='East', name='West', name='Both'
要么
ORDER BY
CASE
WHEN name='East' THEN 1
WHEN name='West' THEN 2
WHEN name='Both' THEN 3
ELSE 4
END;
但是，Postgres抱怨：
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.
我有其他选择吗？
将其包装在派生表中（这是“提示：...。或将UNION移入FROM子句”的建议）
select *
from (
... your union goes here ...
) t
order by
CASE
WHEN name='East' THEN 1
WHEN name='West' THEN 2
WHEN name='Both' THEN 3
ELSE 4
END;
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我来说两句