Question

由于mysql中的TIMESTAMP存储为32位值，表示从1970-jan-1 0:00:00（以秒为单位）的时间间隔，我假设在TIMESTAMP值上使用减号（ - ）运算符会给出这些值的差异很快。实际上不是：

+---------------------------------------------------------------------+
| TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:29:59") |
+---------------------------------------------------------------------+
| 41.000000                                                           |
+---------------------------------------------------------------------+
1 row in set (0.05 sec)

mysql> select timestampdiff(SECOND,TIMESTAMP("2010-04-02 10:30:00"),TIMESTAMP("2010-04-02 10:29:59"));
+-----------------------------------------------------------------------------------------+
| timestampdiff(SECOND,TIMESTAMP("2010-04-02 10:30:00"),TIMESTAMP("2010-04-02 10:29:59")) |
+-----------------------------------------------------------------------------------------+
| -1                                                                                      |
+-----------------------------------------------------------------------------------------+

mysql> select TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:30:01") ;
+---------------------------------------------------------------------+
| TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:30:01") |
+---------------------------------------------------------------------+
| -1.000000                                                           |
+---------------------------------------------------------------------+

+---------------------------------------------------------------------+
| TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:31:00") |
+---------------------------------------------------------------------+
| -100.000000                                                         |
+---------------------------------------------------------------------+

似乎一分钟的差异是100而不是60。

为什么会这样？

Answer 1

只是一个疯狂的猜测，但也许你在三种情况下将字符串转换为整数？

20100402103000 - 20100402103100 = -100

20100402103000 - 20100402103001 = -1

20100402103000 - 20100402102959 = 41

另一种情况是正确转换。

Answer 2

使用的正确函数是UNIX_TIMESTAMP()。

TIMESTAMP()返回日期（时间），格式为'2003-12-31 00:00:00'。

此外，使用

也没有错

SELECT TIMESTAMPDIFF(SECOND,NOW(),TIMESTAMP("2010-04-02 19:29:59"));

Answer 3

我尝试了以下操作并收到NULL

SELECT TIMESTAMPDIFF(SECOND, TIMESTAMP("stopTime"), TIMESTAMP("startTime")) FROM 
paktime WHERE fs = 1 AND employ LIKE "Mike Fowler"

为什么减号运算符给出的结果与mysql中的TIMESTAMPDIFF（）函数不同？

3 个答案: