شباب عايز شرح عن الexists والpair wise والreguler expression
يعني اي هي وظيفة كل واحد ومنها

Exists is logical condition which return true of select return data otherwise it returns false

ie - select * from emp where exists(select deptno from dept)

Pairwise is used with IN operators when you collect more than column in select used in IN operator

ie

SELECT employee_id, manager_id, department_id
 FROM employees
WHERE (manager_id, department_id) IN
             (SELECT manager_id, department_id
                FROM employees
               WHERE first_name = [color="navy"]'John'[/color])
  AND first_name != [color="navy"]'John'[/color];

Regular expression is used to search by pattern not by exact search

you can use it with below function

REGEX_SUBSTR

REGEX_INSTR

you can read from oracle documentation about patterns because it has a lot of pattern which is too long to illustrate here

Thank you