Question

我有一张表（t1）：

id  |    from              |      to               |   item   |   price   |
1      2014-03-14 00:00:00    2014-03-26  00:00:00      25         75
2      2014-03-27 00:00:00       NULL                   25         50
3      2014-03-27 00:00:00    2014-04-01  00:00:00      26         80 
4      2014-04-02 00:00:00       NULL                   26         100

现在，如果是item = 25，我想选择t1.id = 2。在这种情况下，日期为2014-03-27和NULL，因为不知道此价格何时结束。

如果是item = 26，我希望在4月1日之前获得t1.id = 3，从4月2日开始t1.id = 4。

我该如何撰写查询？

修改

查询的想法：

SELECT `from`, IF(`to` IS NOT NULL, `to`, NOW()), price, item
  FROM t1
WHERE NOW() BETWEEN `from` 
            AND IF(`to` IS NOT NULL,
                   `to`,
                   NOW()
                )
ORDER BY item

今天（3月31日）的预期结果：

id  |    from              |      to               |   item   |   price   |
2      2014-03-27 00:00:00       NULL                   25         50
3      2014-03-27 00:00:00    2014-04-01  00:00:00      26         80

4月3日的预期结果：

id  |    from              |      to               |   item   |   price   |
2      2014-03-27 00:00:00       NULL                   25         50
4      2014-04-02 00:00:00       NULL                   26         100

Answer 1

您可以在select语句中包含列to并避免使用if表达式。

SELECT 
  id, `from`, `to`, price, item
FROM t1
WHERE NOW() BETWEEN 
            `from` AND IF(`to` IS NOT NULL, `to`, NOW() )
ORDER BY item;

对于任何未来的目标日期记录，

set @future_date := now() + interval 3 day;

SELECT 
  id, `from`, `to`, price, item, @future_date
FROM t1
WHERE @future_date BETWEEN `from`
                   AND IF(`to` IS NOT NULL, `to`, @future_date )
ORDER BY item;

演示 @ SQL Fiddle

Answer 2

这就是它的工作原理

SELECT `from`, `to`, item, price
    FROM t1
    WHERE NOW() BETWEEN `from` AND `to`
    OR `from` <= NOW() AND ISNULL(`to`)
    ORDER BY item;

并证明它将来有效，这是4月3日的另一个问题

SELECT `from`, `to`, item, price
    FROM t1
    WHERE '2014-04-03' BETWEEN `from` AND `to`
    OR `from` <= '2014-04-03' AND ISNULL(`to`)
    ORDER BY item;

这是 SQL Fiddle

一切都很清楚？

mysql从DB中选择日期，其中t1.from和t1.to之间的NOW（）与t1.to未定义

2 个答案: