Oracle的REGEXP_SUBSTR函数简单用法

REGEXP_SUBSTR延伸SUBSTR函数的功能，让你搜索一个正则表达式模式字符串。

这也类似于REGEXP_INSTR，而是返回子字符串的位置，它返回的子字符串本身。

语法

Oracle数据库中的REGEXP_SUBSTR函数的语法是：

REGEXP_SUBSTR(source_char, pattern [, position [, occurrence [, match_parameter ]]])

参数

source_char

搜索字符串。可以是任意的数据类型char，VARCHAR2，nchar，CLOB，NCLOB类型

pattern

正则表达式

Value	Description
^	Matches the beginning of a string. If used with a match_parameter of ‘m’, it matches the start of a line anywhere within expression.
$	Matches the end of a string. If used with a match_parameter of ‘m’, it matches the end of a line anywhere within expression.
*	匹配零个或多个.
+	匹配一个或多个出现.
?	匹配零次或一次出现.
.	匹配任何字符，除了空.
|	Used like an "OR" to specify more than one alternative.
[ ]	Used to specify a matching list where you are trying to match any one of the characters in the list.
[^ ]	Used to specify a nonmatching list where you are trying to match any character except for the ones in the list.
( )	Used to group expressions as a subexpression.
{m}	Matches m times.
{m,}	Matches at least m times.
{m,n}	Matches at least m times, but no more than n times.
	n is a number between 1 and 9. Matches the nth subexpression found within ( ) before encountering .
[..]	Matches one collation element that can be more than one character.
[::]	Matches character classes.
[==]	Matches equivalence classes.
d	匹配一个数字字符.
D	匹配一个非数字字符.
w	匹配包括下划线的任何单词字符.
W	匹配任何非单词字符.
s	匹配任何空白字符，包括空格、制表符、换页符等等.
S	匹配任何非空白字符.
A	Matches the beginning of a string or matches at the end of a string before a newline character.
	Matches at the end of a string.
*?	Matches the preceding pattern zero or more occurrences.
+?	Matches the preceding pattern one or more occurrences.
??	Matches the preceding pattern zero or one occurrence.
{n}?	Matches the preceding pattern n times.
{n,}?	Matches the preceding pattern at least n times.
{n,m}?	Matches the preceding pattern at least n times, but not more than m times.

position

可选。搜索在字符串中的开始位置。如果省略，默认为1，这是第一个位置的字符串。

occurrence

可选。它是模式字符串中的第n个匹配位置。如果省略，默认为1。

match_parameter

可选。它允许你修改regexp_substr功能匹配的行为。它可以是以下的组合：

Value	Description
‘c’	区分大小写的匹配.
‘i’	不区分大小写的匹配.
‘n’	Allows the period character (.) to match the newline character. By default, the period is a wildcard.
‘m’	expression is assumed to have multiple lines, where ^ is the start of a line and $ is the end of a line, regardless of the position of those characters in expression. By default, expression is assumed to be a single line.
‘x’	Whitespace characters are ignored. By default, whitespace characters are matched like any other character.

Examples

找出匹配的数字

SELECT REGEXP_SUBSTR ("hello my phone is 520 ", "[0-9]+") FROM dual; --520

下面这个例子返回指定第三次出现的字符

SELECT REGEXP_SUBSTR ("i like beijing tiananmen", "(S*)(s)", 1, 3)
FROM dual;    --beijing

作者：itmyhome