Regular Expression In Oracle SQL 2 | Regexp_Count in Oracle SQL

Queries:
Select last_name,regexp_count(last_name,'[A-K]') from employees;
Select first_name,regexp_count(first_name,'[A-K]',1,'i') from employees;
Select first_name,regexp_count(first_name,'^[A-C]') from employees;
Select last_name,regexp_count(last_name,'K.[a-z]') from employees;
Select last_name,regexp_count(last_name,'K(.{2,3})[a-z]$') from employees;
Select regexp_count ('REGEXP_COUNT is introduced in the Oracle version 11gR1', '\d', 1) regexp_count from dual;
Select regexp_count ('REGEXP_COUNT is introduced in the Oracle version 11gR1', '\d', 51) regexp_count from dual;