使用别名从两个表格前5中选择

Question

我如何从两个表中选择datetime（dt）并按日期时间获取最后5个条目。

SELECT TOP 5, Table1.dt AS DT, Table2.dt AS TD FROM Table1, Table2 ORDER BY dt DESC LIMIT 5

表1条目DT：

2018-04-11 13:09:23
2018-04-12 13:09:23
2018-04-19 13:09:23
2018-04-21 13:09:23
2018-04-29 13:09:23
2018-04-29 15:09:23

表2条目DT：

2018-04-11 13:09:23 
2018-04-12 13:09:23
2018-04-18 13:09:23
2018-04-21 13:09:23
2018-04-29 13:09:23
2018-04-29 15:09:23

它来自两个表TOP 5 ORDER BY datetime（dt）：

2018-04-11 13:09:23 DT
2018-04-11 13:09:23 TD
2018-04-12 13:09:23 DT
2018-04-12 13:09:23 TD
2018-04-18 13:09:23 TD

Answer 1

您想要UNION，而不是跨产品。

SELECT dt, 'DT' AS which
FROM Table1
UNION ALL
SELECT dt, 'TD' AS which
FROM Table2
ORDER BY dt DESC
LIMIT 5