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oracle的TO_NUMBER函数

TO_NUMBER(x [, format], [ nls_language ]) converts x to a NUMBER.

x is the string that will be converted to a number.　　x是将要被转换成number的字符串。
format, optional, is the format that will be used to convert x to a number. format，可选项，是用来将x转换成number的格式。
nls_language, optional, is the nls language used to convert x to a number. nls_language，可选项，是nls语言，用来将x转换成number。

Number Format Elements:

Element	Example	Description
, .	1,234.56	Commas and decimal points 逗号和小数点
$	$123.45	Leading dollar sign. 前置$符号
0	0012.34	Leading or trailing 0. 前置或后置0
9	123	Any digit. 任意数字
B	B123	Leading blank for integers. integer类型前置空白符
C	C123	The ISO currency symbol defined in the NLS_ISO_CURRENCY parameter.定义在NLS_ISO_CURRENCY参数中的国际标准货币符号
D	123D99	The current decimal character defined in the NLS_NUMERIC_CHARACTERS parameter. The default value is a period.
EEEE	1.2EEE	Returns a value in scientific notation.用科学计数法表示返回值
G	9G123	Returns the group separator (e.g., a comma).
L	L123	Returns the local currency symbol.
MI	123MI	negative value with trailing minus sign; returns positive value with a trailing blank.
PR	123PR	The negative values in angle brackets.
RN	I	values in Roman numerals, uppercase.
rn	i	values in Roman numerals, lowercase.
S (prefix)	S1234	negative values with a leading minus sign, positive values with a leading positive sign.
S (suffix)	1234S	negative values with a trailing minus sign, positive values with a trailing positive sign.
TM	TM	The text minimum number format model returns the smallest number of characters possible.
U	U123	the Euro currency symbol or the NLS_DUAL_CURRENCY parameter.
V	123V99	a value multiplied by 10n, where n is the number of 9s after the V.
X	XXXX	the hexadecimal value.十六进制值


SQL> select to_number(‘123.45‘) from dual;

TO_NUMBER(‘123.45‘)
-------------------
             123.45

SQL> select to_number(‘123.45‘, ‘9999.99‘) from dual;

TO_NUMBER(‘123.45‘,‘9999.99‘)
-----------------------------
                       123.45

SQL> select to_number(‘12‘, ‘99‘) from dual;

TO_NUMBER(‘12‘,‘99‘)
--------------------
                  12

SELECT TO_NUMBER(‘$12,123.23‘,‘$999,999.99‘) FROM DUAL;

SQL>
SQL>
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Do calculation after the conversion


SQL> select to_number(‘123.45‘) + 2 from dual;

TO_NUMBER(‘123.45‘)+2
---------------------
               125.45

SQL> SELECT TO_NUMBER(‘-$12,345.67‘, ‘$99,999.99‘) FROM dual;

TO_NUMBER(‘-$12,345.67‘,‘$99,999.99‘)
-------------------------------------
                            -12345.67

SQL>

文章来自：http://www.cnblogs.com/itzfz/p/5583185.html