您可以union
在不同时间进行几个查询:
(SELECT id, a_time AS time, Metadata1, Metadata2
FROM mytable)
UNION
(SELECT id, b_time AS time, Metadata1, Metadata2
FROM mytable)
UNION
(SELECT id, c_time AS time, Metadata1, Metadata2
FROM mytable)
UNION
(SELECT id, d_time AS time, Metadata1, Metadata2
FROM mytable)
ORDER BY time