Question

我有一个带有TIME列的数据库，我想将该时间的舍入版本与另一个表中的TIME列进行比较。

Example:

root@localhost (mytest) desc ss;
+-------+------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------+------+-----+---------+-------+
| t     | time | YES  |     | NULL    |       | 
+-------+------+------+-----+---------+-------+
1 row in set (0.01 sec)

root@localhost (mytest) desc tt;
+-------+------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------+------+-----+---------+-------+
| s     | time | YES  |     | NULL    |       | 
+-------+------+------+-----+---------+-------+
1 row in set (0.00 sec)

root@localhost (mytest) select * from ss;
+----------+
| t        |
+----------+
| 16:00:00 | 
+----------+
1 row in set (0.00 sec)

root@localhost (mytest) select * from tt;
+----------+
| s        |
+----------+
| 15:45:00 | 
| 16:00:00 | 
| 19:30:00 | 
| 17:45:00 | 
| 18:00:00 | 
| 19:30:00 | 
+----------+

需要一个查询来连接ss和tt，其中舍入为tt.s = ss.t

Answer 1

尝试：

SELECT * FROM tt JOIN ss ON HOUR(tt.s) = HOUR(ss.t);

结帐MySQL Date/Time Functions

Answer 2

我的解决方案是转换为秒，进行数学计算，然后转换回TIME。

select s,hour(s)*3600+minute(s)*60+second(s) time_as_seconds from tt;
+----------+-----------------+
| s        | time_as_seconds |
+----------+-----------------+
| 15:45:00 |           56700 | 
| 16:00:00 |           57600 | 
| 19:30:00 |           70200 | 
| 17:45:00 |           63900 | 
| 18:00:00 |           64800 | 
| 19:30:00 |           70200 | 
+----------+-----------------+
6 rows in set (0.00 sec)

对于一个小数据集，我只计算每个表中的“秒”值并进行比较。所以我最终加入了：

1800 * round((hour(tt.s)*3600+minute(tt.s)*60+second(tt.s)) / 1800)

针对

hour(ss.t)*3600+minute(ss.t)*60+second(ss.t)

但是如果引用表（t）中有很多行，或者t.ss上有一个可以加速查询的索引，那么我们必须得到时间值。 SEC_TO_TIME解决了这个问题。

所以，这是一个四舍五入到最近半小时（因此是1800）的例子

select 
 s, 
 hour(s)*3600+minute(s)*60+second(s) time_as_seconds,
 1800 * round((hour(s)*3600+minute(s)*60+second(s)) / 1800) rounded_to_half_hour,
 sec_to_time(1800 * round((hour(s)*3600+minute(s)*60+second(s)) / 1800)) rounded_time
from tt;

+----------+-----------------+----------------------+--------------+
| s        | time_as_seconds | rounded_to_half_hour | rounded_time |
+----------+-----------------+----------------------+--------------+
| 15:45:00 |           56700 |                57600 | 16:00:00     | 
| 16:00:00 |           57600 |                57600 | 16:00:00     | 
| 19:30:00 |           70200 |                70200 | 19:30:00     | 
| 17:45:00 |           63900 |                64800 | 18:00:00     | 
| 18:00:00 |           64800 |                64800 | 18:00:00     | 
| 19:30:00 |           70200 |                70200 | 19:30:00     | 
+----------+-----------------+----------------------+--------------+
6 rows in set (0.00 sec)

Answer 3

假设ss.t已经四舍五入：

SELECT *
FROM tt
  JOIN ss
  ON    ( SUBTIME(ss.t, '00:30:00.0') <= tt.s )
    AND ( tt.s < ADDTIME(ss.t, '00:30:00.0')  )

如何将MySQL TIME舍入到最近的小时（不是DATE TIME / TIMESTAMP）

3 个答案: