Oracle的REGEXP_REPLACE函数简单用法

REGEXP_REPLACE让你搜索的字符串的正则表达式模式REPLACE函数的功能。默认情况下，

该函数返回source_char与replace_string取代了正则表达式模式的每个实例。

返回的字符串是在相同的字符集source_char。

语法

Oracle数据库中的REGEXP_REPLACE函数的语法是：

REGEXP_REPLACE(source_char, pattern [, replace_string [, position [, occurrence [, match_parameter ] ] ] ] )

参数

source_char

搜索值的字符表达式。这通常是一个字符列，可以是任何数据类型CHAR，VARCHAR2，NCHAR，NVARCHAR2，CLOB或NCLOB。

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	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.
\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.

replace_string

可选。匹配的模式将被替换replace_string字符串。如果省略replace_string参数，

将删除所有匹配的模式，并返回结果字符串。

position

可选。在字符串中的开始位置搜索。如果省略，则默认为1。

occurrence

可选。是一个非负整数默认为1，指示替换操作的发生：

如果指定0，那么所有出现将被替换字符串。

如果指定了正整数n，那么将替换第n次出现。

match_parameter

可选。它允许你修改REGEXP_REPLACE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.

EXAMPLE - 匹配第一个字

让我们开始使用REGEXP_REPLACE函数替换字符串中的第一个字。

For example:

SELECT REGEXP_REPLACE ('itmyhome is my network id', '^(\S*)', 'luck')
FROM dual;

Result: luck is my network id

这个例子会返回”luck is my network id”，

因为它会再字符串的开始找到第一个匹配的字符，然后替换为”luck”

EXAMPLE - 匹配数字字符

我们将使用REGEXP_REPLACE函数来匹配单个数字字符模式。

For example:

SELECT REGEXP_REPLACE ('2, 5, and 10 are numbers in this example', '\d', '#')
FROM dual;

Result: '#, #, and ## are numbers in this example'

此示例将所指定的

\d

数字将以#字符替换

我们可以改变我们的正则模式来搜索仅两位数字。

For example:

SELECT REGEXP_REPLACE ('2, 5, and 10 are numbers in this example', '(\d)(\d)', '#')
FROM dual;

Result: '2, 5, and # are numbers in this example'

这个例子将替换具有两个数字并排指定的

(\d)(\d)

模式。在这种情况下，它将跳过2和5个数字值和用#字符替换10。

作者：itmyhome