select phone_number, substr(phone_number, instr(phone_number, '.', 1,1)+1, instr(phone_number, '.', 1,2)-instr(phone_number, '.', 1,1)) melumat from hr.employees;
select phone_number, substr(phone_number, instr(phone_number, '.', 1,1)+1, instr(phone_number, '.', 1,2)-instr(phone_number, '.', 1,1)-1) melumat from hr.employees;
#replace SELECT phone_number, replace(phone_number,'.','') from hr.employees; SELECT phone_number, length(phone_number) - length(replace(phone_number,'.','')) from hr.employees;
SELECT phone_number, CASE WHEN instr(phone_number,'.',1,3) <> 0 then substr(phone_number, instr(phone_number, '.',1,1)+1, instr(phone_number, '.',1,2)-instr(phone_number, '.',1,1)-1) else phone_number end yeni from hr.employees
#JOIN
SELECT emp.employee_id, emp.first_name, emp.department_id, dep.department_name FROM hr.employees emp JOIN hr.departments dep ON emp.department_id = dep.department_id; select dep.* emp.first_name from hr.departments dep left join hr.employees employeeson dep.department_id = emp.departmen_id ;