CREATE TABLE job_history (EMPLOYEE_ID NUMBER, START_DATE DATE, END_DATE DATE, JOB_ID VARCHAR2, DEPARTMENT_ID NUMBER)
CREATE TABLE locations (LOCATION_ID NUMBER, STREET_ADDRESS VARCHAR2, POSTAL_CODE VARCHAR2, CITY VARCHAR2, STATE_PROVINCE VARCHAR2, COUNTRY_ID VARCHAR2)
CREATE TABLE jobs (JOB_ID VARCHAR2, JOB_TITLE VARCHAR2, MIN_SALARY NUMBER, MAX_SALARY NUMBER)
CREATE TABLE countries (COUNTRY_ID VARCHAR2, COUNTRY_NAME VARCHAR2, REGION_ID NUMBER)
CREATE TABLE employees (EMPLOYEE_ID NUMBER, FIRST_NAME VARCHAR2, LAST_NAME VARCHAR2, EMAIL VARCHAR2, PHONE_NUMBER VARCHAR2, HIRE_DATE DATE, JOB_ID VARCHAR2, SALARY NUMBER, COMMISSION_PCT NUMBER, MANAGER_ID NUMBER, DEPARTMENT_ID NUMBER)
CREATE TABLE departments (DEPARTMENT_ID NUMBER, DEPARTMENT_NAME VARCHAR2, MANAGER_ID NUMBER, LOCATION_ID NUMBER)
CREATE TABLE regions (REGION_ID NUMBER, REGION_NAME VARCHAR2)

Give the name of each department and the number of employees in each. Plot them as bar chart.
SELECT DEPARTMENT_NAME, COUNT(*) FROM employees AS T1 JOIN departments AS T2 ON T1.DEPARTMENT_ID = T2.DEPARTMENT_ID GROUP BY T2.DEPARTMENT_NAME
SELECT "DEPARTMENT_NAME", COUNT(*) FROM "employees" "T1" JOIN "departments" "T2" ON "T1"."DEPARTMENT_ID" = "T2"."DEPARTMENT_ID" GROUP BY "T2"."DEPARTMENT_NAME"