Can you format 24-hour time string into 12-hour time string with AM/PM?

问题:

I store some time values in sqlite in %H:%M string format (for example "15:43"), but I would like to get them out formatted in 12 hour format with AM/PM indicators (for example "3:43 PM"). Is this possible with sqlite (and if so, how), or do I need to do this in my application code?

回答1:

Unless you extend sqlite with your own custom function, you'll have to do this is code.

sqlite's strftime date formatting function only supports a small subset of its C counterpart, insufficient for your problem. sqlite also lacks a selection construct like IF or CASE, making simple if/else impossible.

回答2:

Some pseudo code to help you on the way:

if (hourpart of time >= 12)     subtract 12 from hours     append string " pm" else // hourpart < 12     append string " am" end if 

In SQL you can accomplish this using the CASE syntax.

---

After taking a closer look at the problem:

SELECT (CASE HOUR(myTimeColumn) >= 12 WHEN 1 THEN          ((HOUR(myTimeColumn) - 12) + '-' + MINUTE(myTimeColumn) + ' pm')        ELSE          (HOUR(myTimeColumn) + '-' + MINUTE(myTimeColumn) + ' am')        AS AmPmTime,        someOtherColumn FROM myTable 

I'm not entirely sure that all of that is valid SQLite syntax, but you should be able to correct the bugs.

回答3:

There are a few special situation that are covered here. I'm using 'now' as a source, but you can adjust it for your string:

select   CASE    --For 00:05, for example.   WHEN (strftime('%H', 'now', 'localtime') - 12) = -12   THEN  '12:' || strftime('%M', 'now', 'localtime') ||' '|| 'AM'   --For 12:05, for example.   WHEN (strftime('%H', 'now', 'localtime') - 12) = 0   THEN '12:' || strftime('%M', 'now', 'localtime') ||' '|| 'PM'   --other am time   WHEN (strftime('%H', 'now', 'localtime') - 12) < 0   THEN  strftime('%H', 'now', 'localtime') ||':'||     strftime('%M', 'now', 'localtime') ||' '|| 'AM'   ELSE   --other pm time     (cast(strftime('%H', 'now', 'localtime') as integer) - 12) ||':'||     strftime('%M', 'now', 'localtime') ||' '|| 'PM'   END here_you_go_usa; 

回答4:

Do it in your application. Store it in normal 24h format in the database. In the database it can be stored as a Date entry instead of a string (correct me if im wrong)

回答5:

As PoweRoy recomended, this belongs in the application.

It is recommended that any kind of data stored of used in communication uses a standard, locale-insensitive format: http://www.mihai-nita.net/article.php?artID=20051025a

回答6:

Here's a working one.. Thanks to Tomas

SELECT      PatientName,      CASE WHEN          StrFTime('%H', AppointmentTime) % 12 = 0 THEN 12         ELSE StrFTime('%H', AppointmentTime) % 12 END      || ':' ||         StrFTime('%M', AppointmentTime)     || ' ' ||     CASE WHEN         StrFTime('%H', AppointmentTime) > 12 THEN 'PM'         ELSE 'AM' END        `APP_TIME` From Patients;       

OUTPUT
Abdul Salim, 12:05 PM

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