正则函数 regexp_replace

with a as
(
select 'abcdeft' as a1 from dual
union all
select 'aaabbb' as a1 from dual
)
select regexp_replace(a.a1,'(...)(.+$)','\1123\2') from a;

REGEXP_REPLACE(A.A1,'(...)(.+$
--------------------------------------------------------------------------------
abc123deft
aaa123bbb



with a as
(
select 'abcdeft' as a1 from dual
union all
select 'aaabbb' as a1 from dual
union all
select 'a' as a1 from dual
)
select regexp_replace(a.a1,'(...)(.+$)','\1123\2') from a;

REGEXP_REPLACE(A.A1,'(...)(.+$
--------------------------------------------------------------------------------
abc123deft
aaa123bbb
a