Oracle to_char的用法

The following are number examples for the to_char function.

to_char(1210.73, '9999.9')	would return '1210.7'
to_char(1210.73, '9,999.99')	would return '1,210.73'
to_char(1210.73, '$9,999.00')	would return '$1,210.73'
to_char(21, '000099')	would return '000021'

 

The following is a list of valid parameters when the to_char function is used to convert a date to a string. These parameters can be used in many combinations.

Parameter	Explanation
YEAR	Year, spelled out
YYYY	4-digit year
YYY YY Y	Last 3, 2, or 1 digit(s) of year.
IYY IY I	Last 3, 2, or 1 digit(s) of ISO year.
IYYY	4-digit year based on the ISO standard
Q	Quarter of year (1, 2, 3, 4; JAN-MAR = 1).
MM	Month (01-12; JAN = 01).
MON	Abbreviated name of month.
MONTH	Name of month, padded with blanks to length of 9 characters.
RM	Roman numeral month (I-XII; JAN = I).
WW	Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.
W	Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.
IW	Week of year (1-52 or 1-53) based on the ISO standard.
D	Day of week (1-7).
DAY	Name of day.
DD	Day of month (1-31).
DDD	Day of year (1-366).
DY	Abbreviated name of day.
J	Julian day; the number of days since January 1, 4712 BC.
HH	Hour of day (1-12).
HH12	Hour of day (1-12).
HH24	Hour of day (0-23).
MI	Minute (0-59).
SS	Second (0-59).
SSSSS	Seconds past midnight (0-86399).
FF	Fractional seconds.

 

The following are date examples for the to_char function.

to_char(sysdate, 'yyyy/mm/dd');	would return '2003/07/09'
to_char(sysdate, 'Month DD, YYYY');	would return 'July 09, 2003'
to_char(sysdate, 'FMMonth DD, YYYY');	would return 'July 9, 2003'
to_char(sysdate, 'MON DDth, YYYY');	would return 'JUL 09TH, 2003'
to_char(sysdate, 'FMMON DDth, YYYY');	would return 'JUL 9TH, 2003'
to_char(sysdate, 'FMMon ddth, YYYY');	would return 'Jul 9th, 2003'

 

You will notice that in some examples, the format_mask parameter begins with "FM". This means that zeros and blanks are suppressed. This can be seen in the examples below.

to_char(sysdate, 'FMMonth DD, YYYY');	would return 'July 9, 2003'
to_char(sysdate, 'FMMON DDth, YYYY');	would return 'JUL 9TH, 2003'
to_char(sysdate, 'FMMon ddth, YYYY');	would return 'Jul 9th, 2003'

The zeros have been suppressed so that the day component shows as "9" as opposed to "09".

Oracle函數to_char轉化數字型指定小數點位數的用法

to_char，函數功能，就是將數值型或者日期型轉化為字符型。

比如最簡單的應用：

/*1.0123--->'1.0123'*/ 
Select TO_CHAR(1.0123) FROM DUAL 
/*123--->'123'*/ 
Select TO_CHAR(123) FROM DUAL

 接下來再看看下面：

/*0.123 ---> '.123' */ 
SELEC TO_CHAR(0.123) FROM DUAL

 上面的結果 '.123' 在大多數情況下都不是我們想要的結果，我們想要的應該是 '0.123'。

我們來看一下to_char函數的具體用法：

TO_CHAR ( n [, fmt [, 'nlsparam']] )

該函數將NUMBER類型的n按數值格式fmt轉換成VARCHAR2類型的值。'nlsparams'指定由數值格式的元素返回的字符,包括: 

．小數點字符 

．組分隔符 

．本地錢幣符號 

．國際錢幣符號 

變元的形式為： 

'NLS_NUMERIC_CHARACTERS="dg" NLS_CURRENCY="tcxt" NLS_ISO_CURRENCY=territory' 

其中d為小數點字符,g為組分隔符。 

例 :TO_CHAR (17145,'L099G999','NLS_NUMERIC_CHARACTERS=".," NLS_CURRENCY="NUD"')=NUD017,145

通過上面的了解，再查看fmt的一些格式，我們可以用以下表達式得到'0.123'的值：

/*0.123 ---> ' 0.123' */  
Select TO_CHAR(0.123,'0.999') FROM DUAL 
/*100.12 ---> '######' */  
Select TO_CHAR(100.12,'0.999') FROM DUAL 
/*1.12 ---> ' 1.120' */  
Select TO_CHAR(1.12,'0.999') FROM DUAL

 ' 0.123'是出來了，可是前面又多了一個空格。

對於 100.12 的值卻是######，以及'1.12'的值變成了 '1.120'。

我們重新確定一個新的需求：

1、去空格

2、小數點最多4位，最少保留2位。

    1--->'1.00'；1.1--->'1.00'；1.12-->'1.12'；1.1234--->'1.1234'；

    1.12345--->'1.1235'

最終實現如下：

/* 
  FM ：除空格   
  9999999.0099：允許小數點左邊最大正數為7位，小數點右邊最少2位，最多4位，且在第5位進行四舍五入 
*/  
Select TO_CHAR(123.0233,'FM9999999.0099') FROM DUAL

to_char函數特殊用法 

to_char(sysdate,'d') 每周第幾天 
to_char(sysdate,'dd') 每月第幾天 
to_char(sysdate,'ddd') 每年第幾天 
to_char(sysdate,'ww') 每年第幾周 
to_char(sysdate,'mm') 每年第幾月 
to_char(sysdate,'q') 每年第幾季 
to_char(sysdate,'yyyy') 年 

比如要找某個時間為每周第幾天就可以 
SQL> select to_char(to_date('20070101','yyyymmdd'),'d') from dual;

 

 

轉載至：http://blog.csdn.net/aqszhuaihuai/article/details/4051401