将 24 小时制转换为 12 小时制加上 AM/PM 指示 Oracle SQL
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Convert 24 Hour time to 12 Hour plus AM/PM indication Oracle SQL
提问by Galen_GG
I am required to do the following as an exercise, and I am struggling to find a solution:
我需要做以下练习，我正在努力寻找解决方案：
Write a SELECT statement that returns these columns from the Invoices table:
编写一个 SELECT 语句，从 Invoices 表中返回这些列：
The invoice_date column
发票日期列
Use the TO_CHAR function to return the invoice_date column with its full date and time including a four-digit year on a 24-hour clock
使用 TO_CHAR 函数返回 invoice_date 列及其完整的日期和时间，包括 24 小时制的四位数年份
Use the TO_CHAR function to return the invoice_date column with its full date and time including a four-digit year on a 12-hour clock with an am/pm indicator.
使用 TO_CHAR 函数返回invoice_date 列及其完整的日期和时间，包括带有 am/pm 指示器的 12 小时制的四位数年份。
Use the CAST function to return the invoice_date column as VARCHAR2(10)
使用 CAST 函数将 invoice_date 列返回为 VARCHAR2(10)
All I can get is:
我所能得到的是：
select invoice_date, to_char(invoice_date, 'DD-MM-YYYY HH:MM:SS') "Date 24Hr"
from invoices
Which gets my first two columns, however I can't figure out any way to select the third column. Any help would be great, thanks. (And yes, this is from my school textbook)
这得到了我的前两列，但是我想不出任何方法来选择第三列。任何帮助都会很棒，谢谢。（是的，这是我的学校教科书）
回答by ruakh
For the 24-hour time, you need to use HH24instead of HH.
对于 24 小时制，您需要使用HH24代替HH。
For the 12-hour time, the AM/PM indicator is written as A.M.(if you want periods in the result) or AM(if you don't). For example:
对于 12 小时制，AM/PM 指示符写为A.M.（如果您希望结果中包含句点）或AM（如果您不希望）。例如：
SELECT invoice_date,
TO_CHAR(invoice_date, 'DD-MM-YYYY HH24:MI:SS') "Date 24Hr",
TO_CHAR(invoice_date, 'DD-MM-YYYY HH:MI:SS AM') "Date 12Hr"
FROM invoices
;
For more information on the format models you can use with TO_CHARon a date, see http://docs.oracle.com/cd/E16655_01/server.121/e17750/ch4datetime.htm#NLSPG004.
有关可用于TO_CHAR日期的格式模型的更多信息，请参阅http://docs.oracle.com/cd/E16655_01/server.121/e17750/ch4datetime.htm#NLPG004。
