Oracle-函数-替换字符串

REPLACE(char,search_string,replacement_string)

1991' is search_string
'2001' is replacement_string
REPLACE returns char with every occurrence of search_string replaced with replacement_string. 
If replacement_string is omitted or null, then all occurrences of search_string are removed. 
If search_string is null, then char is returned.
REPLACE的实现是由TRANSLATE函数为基础，在REPLACE中，原值和被替换项与替换后的项数据类型支持：CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB

SELECT REPLACE('2301231991','1991','2001') FROM DUAL;
执行结果为：'2301232001'

TRANSLATE(char, from_string, to_string)

--' */''' is from_strin
--'_'     is to_string
--被替换项从左至右依次替换，替换项按照使用个数递减，若替换项不足则替换为''
SELECT TRANSLATE('SQL*Plus User''s Guide', ' */''', '_') FROM DUAL;
--执行结果为：SQLPlus_Users_Guide
SELECT TRANSLATE('SQL*Plus User''s Guide', ' */''', '__') FROM DUAL;
--执行结果为：SQL_Plus_Users_Guide
SELECT TRANSLATE('SQL*Plus User''s Guide', ' */''', '___') FROM DUAL;
--执行结果为：SQL_Plus_Users_Guide
SELECT TRANSLATE('SQL*Plus User''s Guide', ' */''', '____') FROM DUAL;
--执行结果为：SQL_Plus_User_s_Guide

REGEXP_REPLACE（source_char，match_parameter，replace_string）

--REGEXP_REPLACE的实现是由REPLACE函数为基础，支持正则表达式，可以进行复杂字符处理
SELECT REGEXP_REPLACE('132.546.7890','([[:digit:]]{3})\.([[:digit:]]{3})\.([[:digit:]]{4})','(\1) \2-\3')  FROM DUAL ;
--The following example examines phone_number, looking for the pattern xxx.xxx.xxxx. Oracle reformats this pattern with (xxx) xxx-xxxx.
--执行结果为：(132) 546-7890
SELECT REGEXP_REPLACE('500   Oracle     Parkway,    Redwood  Shores, CA','( ){2,}', ' ') FROM DUAL;
--The following example examines the string, looking for two or more spaces. Oracle replaces each occurrence of two or more spaces with a single space.
--执行结果为：500 Oracle Parkway, Redwood Shores, CA