Oracle的REGEXP_SUBSTR函數簡單用法

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REGEXP_SUBSTR延伸SUBSTR函數的功能，讓你搜索一個正則表達式模式字符串。

這也類似於REGEXP_INSTR，而是返回子字符串的位置，它返回的子字符串本身。

語法

Oracle數據庫中的REGEXP_SUBSTR函數的語法是：

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

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參數

source_char

搜索字符串。可以是任意的數據類型char，VARCHAR2，nchar，CLOB，NCLOB類型

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.
*	匹配零個或多個.
+	匹配一個或多個出現.
?	匹配零次或一次出現.
.	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	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	匹配一個數字字符.
\D	匹配一個非數字字符.
\w	匹配包括下劃線的任何單詞字符.
\W	匹配任何非單詞字符.
\s	匹配任何空白字符，包括空格、製表符、換頁符等等.
\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.
\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

可選。搜索在字符串中的開始位置。如果省略，默認爲1，這是第一個位置的字符串。

occurrence

可選。它是模式字符串中的第n個匹配位置。如果省略，默認爲1。

match_parameter

可選。它允許你修改regexp_substr功能匹配的行爲。它可以是以下的組合：

Value	Description
‘c’	區分大小寫的匹配.
‘i’	不區分大小寫的匹配.
‘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

找出匹配的數字

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

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下面這個例子返回指定第三次出現的字符

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

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作者：itmyhome