Question

我正在选择NOW（）和特定X天间隔之间的所有记录，并遇到了我不理解的奇怪行为。

我正在检查未来24小时和过去24小时：

select * from table where date between NOW() and NOW() + 1 interval day; //works
select * from table where date between NOW() and NOW() - 1 interval day; //no records

但如果我撤消between来电：

select * from table where date between NOW() + 1 interval day AND NOW(); //no records
select * from table where date between NOW() - 1 interval day AND NOW(); //works

为什么一个人打电话给未来的工作，但同样的调用过去不起作用？...如果我反转between参数，相反的行为发生 - 在未来24小时不起作用但在过去24小时工作。

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

在下面添加@TimBiegeleisen说明：

date = '2018-05-30' ;

select * from table where date between NOW() and NOW() + 1 interval day;
     = date >= '2018-05-30' AND 'date <= 2018-05-31'; //true
select * from table where date between NOW() and NOW() - 1 interval day; records
     = date >= '2018-05-30' AND 'date <= 2018-05-29'; //false

和

select * from table where date between NOW() + 1 interval day AND NOW();
     = date >= '2018-05-31' AND date <= '2018-05-30' //false
select * from table where date between NOW() - 1 interval day AND NOW();
     = date >= '2018-05-29' and date <= '2018-05-30'; //true

Answer 1

BETWEEN运算符以某种方式解释：

WHERE date BETWEEN a AND b

意味着：

WHERE date >= a AND date <= b

所以以下两个查询是等价的：

select * from table where date between NOW() and NOW() - interval 1 day;
select * from table where date >= NOW() and date <= NOW() - interval 1 day;

希望您可以在第二个查询中看到WHERE条件永远不会成立，因为日期不能同时大于或等于现在和小于现在减去1同时。

Answer 2

简单地说，

对于SQL： WHERE x between a and b 意

x >= a 和 x <= b

因此，我们有a <= x <= b或a <= b

PS：这只是数学：）

两个日期之间的mysql选择有奇怪的行为

2 个答案: