Oracle的REGEXP_SUBSTR函数简单使用方法

REGEXP_SUBSTR延伸SUBSTR函数的功能。让你搜索一个正則表達式模式字符串。

这也相似于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 ]]])

參数

source_char

搜索字符串。能够是随意的数据类型char。VARCHAR2。nchar，CLOB，NCLOB类型

pattern

正則表達式

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.
.	匹配不论什么字符，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	n is a number between 1 and 9. Matches the nth subexpression found within ( ) before encountering \n.
[..]	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	匹配包含下划线的不论什么单词字符.
\W	匹配不论什么非单词字符.
\s	匹配不论什么空白字符。包含空格、制表符、换页符等等.
\S	匹配不论什么非空白字符.
\A	Matches the beginning of a string or matches at the end of a string before a newline character.
\Z	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。搜索在字符串中的開始位置。假设省略，默觉得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。假设省略。默觉得1。

match_parameter

可选。它同意你改动regexp_substr功能匹配的行为。它能够是以下的组合：

Value	Description
‘c’	区分大写和小写的匹配.
‘i’	不区分大写和小写的匹配.
‘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

以下这个样例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