如何使用 REGEXP_REPLACE 从每一端删除重复的逗号和 trim？

Question

我需要将多个字段连接在一起，这些字段可能为 null，也可能不为 null。我可能会得到一个类似这样的字符串：',c,e,' 我实际上想将其显示为 'c,e'.

我可以通过组合 regexp_replace 和 trim:

with sd as (select 'a,b,c' str from dual union all
            select 'a' str from dual union all
            select null str from dual union all
            select 'a,,,d' from dual union all
            select 'a,,,,e,f,,'from dual union all
            select ',,,d,,f,g,,'from dual)
select str,
       regexp_replace(str, '(,)+', '') new_str,
       trim(both ',' from regexp_replace(str, '(,)+', '')) trimmed_new_str
from   sd;

STR         NEW_STR     TRIMMED_NEW_STR
----------- ----------- ---------------
a,b,c       a,b,c       a,b,c          
a           a           a              

a,,,d       a,d         a,d            
a,,,,e,f,,  a,e,f,      a,e,f          
,,,d,,f,g,, ,d,f,g,     d,f,g

但我觉得它应该一次就可以完成 regexp_replace 只是我一辈子都想不出来怎么办！

可能吗？如果可以，怎么做？

Answer 1

试一试：

with sd as (select 'a,b,c' str union all
            select 'a' union all
            select null union all
            select 'a,,,d' union all
            select 'a,,,,,e,f,,' union all
            select ',,,d,,f,g,,')
select str,
       regexp_replace(str, '(,){2,}', '', 1, 0) new_str,
       trim(both ',' from regexp_replace(str, '(,){2,}', '', 1, 0)) trimmed_new_str
from   sd;

Answer 2

查询：

with sd as (select 'a,b,c' str from dual union all
            select 'a' from dual  union all
            select null from dual union all
            select 'a,,,d,' from dual  union all
            select ',a,,,d' from dual  union all
            select ',a,,,d,' from dual  union all
            select ',,,a,,,d,,,' from dual  union all
            select ',a,,,,,e,f,,' from dual union all
            select ',,d,,f,g,,' from dual )
select str,
       regexp_replace(str, '^,+|,+$|,+(,\w)','') new_str
from   sd;

结果：

str             new_str
-----------------------
a,b,c           a,b,c
a               a
(null)          (null)  
a,,,d,          a,d
,a,,,d          a,d
,a,,,d,         a,d
,,,a,,,d,,,     a,d
,a,,,,,e,f,,    a,e,f
,,d,,f,g,,      d,f,g

模式：

  ^,+       matches commas at the beginning
  |         OR
  ,+$       matches commas at the end
  |         OR
  ,+(,\w)   matches several commas followed by a single comma and a word.

仅将上面的第一个子表达式替换为逗号和单词。

如何使用 REGEXP_REPLACE 从每一端删除重复的逗号和 trim？

How to remove repeated commas and trim from each end using REGEXP_REPLACE?

sql

oracle

regexp-replace