CREATE TABLE job_history (employee_id NUMBER, start_date TIME, end_date TIME, job_id CLOB, department_id NUMBER)
CREATE TABLE regions (region_id NUMBER, region_name CLOB)
CREATE TABLE locations (location_id NUMBER, street_address CLOB, postal_code CLOB, city CLOB, state_province CLOB, country_id CLOB)
CREATE TABLE employees (employee_id NUMBER, first_name CLOB, last_name CLOB, email CLOB, phone_number CLOB, hire_date TIME, job_id CLOB, salary NUMBER, commission_pct NUMBER, manager_id NUMBER, department_id NUMBER)
CREATE TABLE jobs (job_id CLOB, job_title CLOB, min_salary NUMBER, max_salary NUMBER)
CREATE TABLE countries (country_id CLOB, country_name CLOB, region_id NUMBER)
CREATE TABLE departments (department_id NUMBER, department_name CLOB, manager_id NUMBER, location_id NUMBER)

What are the employee ids for employees who have held two or more jobs?
SELECT employee_id FROM job_history GROUP BY employee_id HAVING COUNT(*) >= 2
SELECT "employee_id" FROM "job_history" GROUP BY "employee_id" HAVING COUNT(*) >= 2