SQL & PL/SQL

Hello,

From the query given below, I need to do just get "this" [i.e, I need to just replace whatever is NOT "this" to NULL).

when I tried it like given below, it considers "t" "h" "i" and "s" as separate and replaces each and every one of them - can you please help ?


with q1 as
( select 'test_this_23stay_count' str from dual union
select 'say_thisandthat_s13et_count' from dual )
select str,
regexp_replace(str,'[^(this)]','') new_str
from q1

regards,

Raj