/*

 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