Get a word after specific word using regexp_substr in sql oracle

Question

I have tried

select regexp_substr (\'sys: error: This is a message \'\'123:\'\' for column EMP_NB\', \'[[:alpha:]_]+\',1,9) from dual

I have c

Answer 1

Just anchor the pattern to the end of the string:

select regexp_substr('sys: error: This is a message ''123:'' for column EMP_NB', '[[:alpha:]_]+$')
from dual

Here is a db<>fiddle.

Your example data has a period at the end. If that is part of the string, then you can use regexp_replace():

select regexp_replace(message, '^.*[^[:alpha:]_]([[:alpha:]_]+)[^[:alpha:]_]*$', '\1')
from (select 'sys: error: This is a message ''123:'' for column EMP_NB' as message from dual union all
      select 'sys: error: This is a message ''45346:'' for column EM_NM.' as message from dual union all
      select 'sys: error: This is a message ''78324f9:'' for column DEPT_NO_VL.' as message from dual
     ) x