[英]MySQL timestamp modification, addition, and comparison
I am creating a view that involves a little bit of fiddling with timestamps. 我正在创建一个视图,其中涉及一点时间戳。
I have a table A with timestamps. 我有一个带有时间戳的表A。 The view will process the timestamps to see if each timestamp is within a certain range (9 AM - 5 PM).
该视图将处理时间戳,以查看每个时间戳是否在一定范围内(上午9点至下午5点)。 If the timestamp is within that range, I will fetch data matching the exact time in another table (B).
如果时间戳在该范围内,我将在另一个表(B)中获取与确切时间匹配的数据。 Otherwise, I will fetch the next day (or this day's) first valid time (which is 9 AM) and the corresponding data from there.
否则,我将获取第二天(或今天)的第一个有效时间(即上午9点),并从那里获取相应的数据。
Examples: 例子:
12/28/2012 17:01
-> fetch data from B for 12/29/2012 09:00
, set flag to after
. 12/28/2012 17:01
记录->从B中获取数据, 12/29/2012 09:00
为12/29/2012 09:00
,将标志设置为after
。 12/28/2012 08:59
-> fetch data from B for 12/28/2012 09:00
, set flag to before
. 12/28/2012 08:59
记录->从B中获取数据, 12/28/2012 09:00
为12/28/2012 09:00
,将标志设置为before
。 12/28/2012 09:55
-> fetch data from B for 12/28/2012 09:55
, set flag to null
. 12/28/2012 09:55
记录->从B获取12/28/2012 09:55
数据,并将标志设置为null
。 Here is what I have so far (not working, some in pseudocode). 这是我到目前为止的内容(无法正常工作,有些使用伪代码)。 I mainly don't know how to set the flag based on the comparison and then, based on flag, perform next operation on b - all in one statement.
我主要不知道如何基于比较来设置标志,然后基于标志在b上执行下一步操作-全部在一条语句中。
CREATE VIEW C as
SELECT time, (CASE WHEN (time< '9:00' ) THEN'before'
CASE WHEN(time> '17:00') THEN'after' else null END) AS flag FROM A
//These two should be combined into one create view statement
//The below is utterly wrong, I know, but explains what I mean
SELECT(
CASE WHEN (flag=='before') THEN SELECT * FROM B WHERE B.time = time set hour='9:00'
CASE WHEN(flag=='after') THEN SELECT* FROM B WHERE B.time = time + one day set hour='9:00'
ELSE SELECT* FROM B WHERE B.time = time ) as data
Tested using this fiddle: http://sqlfiddle.com/#!2/15be5/50 使用此小提琴进行了测试: http ://sqlfiddle.com/#!2/ 15be5/50
SELECT
q.time as original_time_check,
q.flag as flag_check,
case q.flag
when 'before' then q.NINE_AM_ON_THE_DAY
when 'after' then q.NINE_AM_THE_NEXT_DAY
else q.time
end as time
FROM
(
SELECT
time,
date(time) + INTERVAL 9 HOUR as NINE_AM_ON_THE_DAY,
date(time) + INTERVAL '1 9' DAY_HOUR as NINE_AM_THE_NEXT_DAY,
case
when time < (date(time) + INTERVAL 9 HOUR) then 'before'
when time < (date(time) + INTERVAL 17 HOUR) then 'in-range'
else 'after'
end as flag
FROM
Your_table
) q
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