Question

为什么我会为这些类似的查询获得不同的结果？

SELECT CASE WHEN CONCAT(2011, '-1-1') BETWEEN '2011-01-01' AND '2011-03-31' THEN 1 ELSE 0 END AS status;
+--------+
| status |
+--------+
|      0 |
+--------+  

SELECT CASE WHEN CONCAT(2011, '-1-1') BETWEEN '2011-1-1' AND '2011-3-31' THEN 1 ELSE 0 END AS status;
+--------+
| status |
+--------+
|      1 |
+--------+

Answer 1

您正在比较字符串，而不是日期。尝试显式转换为所需的数据类型：

SELECT CASE WHEN CAST(CONCAT(2011, '-1-1') AS DATETIME) BETWEEN CAST('2011-01-01' AS DATETIME) AND CAST('2011-03-31' AS DATETIME) THEN 1 ELSE 0 END AS status;

Answer 2

因为您正在比较字符串，而不是日期。

将字符串转换为日期的最简单方法是在DATE（）中包装。

SELECT CASE WHEN DATE(CONCAT(2011, '-1-1'))
            BETWEEN DATE('2011-1-1') AND DATE('2011-3-31')
            THEN 1 ELSE 0 END AS status;

http://dev.mysql.com/doc/refman/5.0/en/datetime.html

您也可以缩短查询时间，因为MySQL本地返回布尔值为1/0。

SELECT DATE(CONCAT(2011, '-1-1'))
            BETWEEN DATE('2011-1-1') AND DATE('2011-3-31') as status;

Answer 3

因为它正在进行字符串比较。你应该使用mysl date函数。

 SELECT CASE WHEN date(CONCAT(2011, '-1-1')) BETWEEN date('2011-1-1') AND date('2011-3-31') THEN 1 ELSE 0 END AS status;

如何检查MySQL中的日期是否在范围内？

3 个答案: