mysql select 两个日期之间有奇怪的行为

Question

我正在选择 NOW() 和特定 X 天间隔之间的所有记录，遇到了这种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

但是如果我反转 between 调用：

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

为什么对未来的调用有效，但对过去的调用无效？...如果我反转 between 参数，则会发生相反的行为 - 24 小时后不起作用未来但确实在过去 24 小时内工作。

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在下面写出@TimBiegeleisen 的解释：

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

意思是：

WHERE date >= a AND date <= b

所以下面两个查询是等价的：

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

希望您能看到在您的第二个查询中 WHERE 条件永远不会为真，因为日期不能同时大于或等于现在和更小比现在同时减一

Answer 2

简单地说，

对于SQL： WHERE x between a and b 意义

x >= a 和 x <= b

因此，我们有 a <= x <= b 或 a <= b

PS：这只是关于数学:)

mysql select 两个日期之间有奇怪的行为

mysql select between two dates has odd behavior

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