为什么 Oracle 的 to_char() 函数要添加空格？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/240182/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Why is Oracle's to_char() function adding spaces?
提问by Igor Drincic
Why is Oracle's to_char()function adding spaces?
oracle的to_char()函数为什么要加空格？
select length('012'),
length(to_char('012')),
length(to_char('12', '000'))
from dual;
3, 3, 4
3, 3, 4
采纳答案by stjohnroe
The format mask that you are using is fixed width and allows for a minus sign
您使用的格式掩码是固定宽度并允许使用减号
回答by Tony Andrews
The extra leading space is for the potential minus sign. To remove the space you can use FM in the format:
额外的前导空格用于潜在的减号。要删除空间，您可以使用以下格式的 FM：
SQL> select to_char(12,'FM000') from dual;
TO_C
----
012
By the way, note that to_char takes a NUMBER argument; to_char('012') is implicitly converted to to_char(to_number('012')) = to_char(12)
顺便说一下，注意 to_char 需要一个 NUMBER 参数；to_char('012') 被隐式转换为 to_char(to_number('012')) = to_char(12)
回答by James Curran
To make the answers given more clear:
为了使给出的答案更清楚：
select '['||to_char(12, '000')||']',
'['||to_char(-12, '000')||']',
'['||to_char(12,'FM000')||']'
from dual
[ 012] [-012] [012]
回答by Jay Neumann
Be aware when using the 'fm' syntax it will not include any values after the decimal place unless specified using zeros. For example:
请注意，使用 'fm' 语法时，除非使用零指定，否则小数位后不会包含任何值。例如：
SELECT TO_CHAR(12345, 'fm99,999.00') FROM dual
returns: '12,345.00'
返回：'12,345.00'
SELECT TO_CHAR(12345, 'fm99,999.99') FROM dual
returns: '12,345.'
返回：'12,345。'
As you can see this would be an issue if you are expecting two zeros after the decimals place (maybe in fee reports for example).
如您所见，如果您期望小数点后有两个零（例如可能在费用报告中），这将是一个问题。
