[20260227]使用trim函数删除前后字符.txt

--//想使用trim函数删除前后字符，缺省仅仅删除空格，如果不是空格写法比较特殊，做1个记录。

1.环境：
SCOTT@book01p> @ ver2
==============================
PORT_STRING                   : x86_64/Linux 2.4.xx
VERSION                       : 21.0.0.0.0
BANNER                        : Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
BANNER_FULL                   : Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
Version 21.3.0.0.0
BANNER_LEGACY                 : Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
CON_ID                        : 0
PL/SQL procedure successfully completed.

2.测试：

SCOTT@book01p> select trim('  aaa,bbb ')||'z' c20 from dual ;
C20
--------------------
aaa,bbbz

--//删除前后空格很简单，直接使用trim函数。

--//如果要删除前后逗号，这样写报错。
SCOTT@book01p> select trim(',,,,aaa,bbb,,,',',')||'z' c20 from dual ;
select trim(',,,,aaa,bbb,,,',',')||'z' c20 from dual
                            *
ERROR at line 1:
ORA-00907: missing right parenthesis

--//要写出如下：
SCOTT@book01p> select trim(',' from  ',,,,aaa,bbb,,,')||'z' c20 from dual ;
C20
--------------------
aaa,bbbz

--//第1个参数仅仅接受1个字符。
SCOTT@book01p> select trim('ab' from  ',,,,aaa,bbb,,,')||'z' c20 from dual ;
select trim('ab' from  ',,,,aaa,bbb,,,')||'z' c20 from dual
       *
ERROR at line 1:
ORA-30001: trim set should have only one character

--//当然还有1个笨的方法使用ltrim+rtrim函数。

SCOTT@book01p> select rtrim(ltrim(',,,,aaa,bbb,,,',','),',')||'z' c20 from dual ;
C20
--------------------
aaa,bbbz