我们如何忽略MySQL DATEDIFF()函数返回的负值？

How can we ignore the negative values return by MySQL DATEDIFF() function?

众所周知，DATEDIFF()函数用于获取两个日期之间的天数差。因此，很有可能它也返回负值。

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mysql> select * from differ;
+------------+-------------+
| OrderDate | WorkingDate |
+------------+-------------+
| 2017-10-22 | 2017-10-29 |
| 2017-10-25 | 2017-10-30 |
| 2017-10-25 | 2017-11-30 |
+------------+-------------+
3 rows in set (0.00 sec)

上面的查询将返回表" differ"中的值。现在，如果有人想获得OrderDate和WorkingDate之间的差，则输出将为负，如下所示：

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mysql> Select DATEDIFF(OrderDate, WorkingDate)AS 'DIFFERENCE IN DAYS' from differ;
+--------------------+
| DIFFERENCE IN DAYS |
+--------------------+
| -7 |
| -5 |
| -36 |
+--------------------+
3 rows in set (0.00 sec)

但是我们可以使用MySQL ABS()函数忽略这些负值，可以按照以下步骤进行操作-

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mysql> Select ABS(DATEDIFF(OrderDate, WorkingDate))AS 'DIFFERENCE IN DAYS' from differ;
+--------------------+
| DIFFERENCE IN DAYS |
+--------------------+
| 7 |
| 5 |
| 36 |
+--------------------+
3 rows in set (0.00 sec)