FROM: http://kirin.javaeye.com/blog/197114
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(shù)to_char轉(zhuǎn)化數(shù)字型指定小數(shù)點(diǎn)位數(shù)的用法
to_char，函數(shù)功能，就是將數(shù)值型或者日期型轉(zhuǎn)化為字符型。
比如最簡單的應(yīng)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(jié)果 '.123' 在大多數(shù)情況下都不是我們想要的結(jié)果，我們想要的應(yīng)該是 '0.123'。
我們來看一下to_char函數(shù)的具體用法：
TO_CHAR ( n [, fmt [, 'nlsparam']] )
該函數(shù)將NUMBER類型的n按數(shù)值格式fmt轉(zhuǎn)換成VARCHAR2類型的值。'nlsparams'指定由數(shù)值格式的元素返回的字符,包括:
．小數(shù)點(diǎn)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(shù)點(diǎn)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(dá)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。
對于 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(shù)點(diǎn)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(shí)現(xiàn)如下：
/*
FM ：除空格
9999999.0099：允許小數(shù)點(diǎn)左邊最大正數(shù)為7位，小數(shù)點(diǎn)右邊最少2位，最多4位，且在第5位進(jìn)行四舍五入
*/
Select TO_CHAR(123.0233,'FM9999999.0099') FROM DUAL
PLSQL小經(jīng)驗(yàn)一、 Oracle的to_char()函數(shù)功能很強(qiáng)大但是在用它格式化數(shù)值型數(shù)據(jù)時應(yīng)該請注意以下幾項(xiàng)。如果是小數(shù)如：0.23這樣的數(shù)據(jù)經(jīng)過to_char后再顯示會變?yōu)?23，如果你為了讓它顯示出原來的0.23的話就得用To_char(要格式化的數(shù)值,’0.999’)保留三個小數(shù)，并顯示但這里就要注意了。他為你截取小數(shù)的時候是四舍五入了。所以如果是要求截掉小數(shù)而不四舍五入的話就應(yīng)該自己寫個函數(shù)截下去后再規(guī)格化。以保證它不四舍五入。
二、 To_char(1.9999,’FM90.0999’)這個函數(shù)規(guī)格化時90.0999的含義是有9的地方如果有數(shù)字就顯示如果沒有數(shù)字就不顯示，有0的地方在沒有數(shù)字的時候也會有０來占位.但這樣做也有一個很大的缺點(diǎn),就是如果是整數(shù)時它也仍然會顯示”.”,不要小瞧這個點(diǎn),一般來講頁面上要顯示的話這個點(diǎn)就是多余的.也給我們造成了不小的麻煩.還要自己再寫函數(shù)來把這個小點(diǎn)搞定.
三、 對于日期型的Oracle倒時提供了一個好的處理方法,可以把日期做成數(shù)值型的.然后再To_char就能顯示出你所需要的類型了.
四、 在使用select into時一定要注意,這種方法你一定要確認(rèn)肯定會有數(shù)據(jù)被查出時才能使用.如果查詢結(jié)果為空時會導(dǎo)致報(bào)錯.還有一種情況是查出來的數(shù)據(jù)是多條也會報(bào)錯.所以應(yīng)該盡量便宜游標(biāo)來做.會減少錯誤產(chǎn)生的機(jī)率.
五、 還有注意一點(diǎn)rownum不支持排序,就是說你想用這個來控制行數(shù)的話就會發(fā)現(xiàn)他沒有按你指定的排序方式顯示.,這是一個很難辦的事.而且如果你用rownum=2這樣的語句來輸出第二行的話也是行不通的. 六、 最惡心的一點(diǎn)是Oracle對null的判斷變態(tài)到極點(diǎn).如果你說某個變量 aa=null它是判斷不出來的.盡管aa的確是空.即使在選擇條件里也是判斷不出來的.不知道為什么,只好用nvl()這個函數(shù)來判斷了.在條件之外可以用 aa is null 來判斷.
六 補(bǔ)充一點(diǎn).就是在寫存儲過程時要注意參數(shù)名不能與數(shù)據(jù)庫字段名相同.否則Oracle會把這個參數(shù)名看成是字段名的,即使你用表的別名區(qū)分也不行.所以起參數(shù)名的時候一定要注意這點(diǎn).了