mysql 按两个 unixtime 列合并排序

Question

Table user 结构：

id(PK)(int)
name(varchar)
time1(int10) unixtime
time2(int10) unixtime

SELECT * FROM `user` ORDER BY `time1` DESC,`time2` DESC


 +------------------------------------------------------+
 | id        | name   |     time1     |     time2       |
 +------------------------------------------------------+
 | 12345     | Joe    |  1405605785   |   1406733506    |
 | 12346     | John   |  1406733506   |                 |
 | 12347     | David  |               |   1405684190    |
 +------------------------------------------------------+

我正在使用这个 sql:

SELECT * FROM `user` ORDER BY `time1` DESC,`time2` DESC

如何合并两列time来排序desc？

============

sagi 的更多示例回复

 +------------------------------------------------------+
 | id        | name   |     time1     |     time2       |
 +------------------------------------------------------+
 | 12345     | Joe    |  1            |   2             |
 | 12346     | John   |  5            |                 |
 | 12347     | David  |               |   4             |
 +------------------------------------------------------+

我想这样排序 (DESC)

John (time = 5)
David (time = 4)
Joe (time  max value = 2)

Answer 1

这称为条件排序使用 CASE EXPRESSION :

SELECT * FROM `user` t
ORDER BY CASE WHEN t.time1 is null THEN t.time2 ELSE t.time1 END DESC

也可以写成：

ORDER BY coalesce(t.time1,t.time2)

你没有提供任何预期的结果，也没有说明结果应该按哪一列排序，以防两个 time1,time2 都不是 NULL，所以我假设你想要它按第一列排序。如果不是这种情况，请将 time1 替换为 time2 .

试试这个：

ORDER BY GREATEST(t.time1,t.time2) DESC

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