MySQL Union 2 选择 1 个表并输出 2 列

Question

我目前有 1 个表和 2 个嵌套选择，我想将两个嵌套选择合并在一起，我希望结果集显示两个不同的列，每个结果集一个（每个嵌套选择一个列）。 IE 三列共 t_stamp, R02AO11, R03AO11。这几天我一直在努力解决这个问题，任何可以帮助我的人都将不胜感激。我找到了这个例子Using SELECT UNION and returning output of two columns from one table，这对我来说没有意义——也许有点过头了。希望它不是太多的重新发布。再次感谢。 =)

Select t_stamp,
MIN(R02AO11) 
FROM
( 
SELECT 
    t_stamp,
    R02AO11
FROM 
    tag_history 
WHERE 
    from_unixtime(floor(unix_timestamp(t_stamp)/60)*60) BETWEEN '2012-11-01                                                                                          00:00:00' AND '2012-11-30 23:59:59' 
    AND (R02AO11 IS NOT NULL AND R02AO11 > 0) 
) AS min_tag_history
GROUP BY LEFT(t_stamp, 10)
UNION ## UNION ALL 
Select t_stamp, 
MIN(R03AO11) 
FROM
( 
SELECT 
    t_stamp,
    R03AO11
FROM 
    tag_history 
WHERE 
    from_unixtime(floor(unix_timestamp(t_stamp)/60)*60) BETWEEN '2012-11-01 00:00:00' AND '2012-11-30 23:59:59' 
    AND (R03AO11 IS NOT NULL AND R03AO11 > 0) 
) AS min_tag_history
GROUP BY LEFT(t_stamp, 10)
ORDER BY t_stamp

Answer 1

是你想多了还是我错过了什么？

SELECT 
    t_stamp,
    MIN(CASE WHEN R02AO11 = 0 THEN NULL ELSE R02AO11 END),
    MIN(CASE WHEN R03A011 = 0 THEN NULL ELSE R03A011 END)
FROM 
    tag_history 
WHERE 
    from_unixtime(floor(unix_timestamp(t_stamp)/60)*60) BETWEEN '2012-11-01                                                                                          00:00:00' AND '2012-11-30 23:59:59' 
GROUP BY LEFT(t_stamp, 10)