mysql命令由两个unixtime列组合在一起

Question

表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 | 
+------------------------------------------------------+ 

我使用这个SQL语句：

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

如何两列的时间相结合，分类说明？

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

为鹭

更多例子回复

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

我想有点像那个（DESC）

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

Answer 1

这是所谓的条件排序使用CASE EXPRESSION：

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

也可以写为：

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

你没有提供任何预期的结果，而你没说由列的结果应该在的情况下，责令两time1,time2不NULL，所以我估计你希望它由第一列排序。如果不是这种情况，请用time2替换time1。

试试这个：

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