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 create public synonym customers for hr.customers;
 
SELECT &1, "&2" FROM &3 WHERE last_name = '&4';

select * from hr.employees t where t.last_name='';
SELECT last_name, salary , hire_date FROM EMPLOYEES ORDER BY salary DESC;
 SELECT last_name, salary , hire_date FROM EMPLOYEES ORDER BY 2 DESC;
 select substr('1234567',0,3) from dual;

 
 SELECT e.last_name, d.department_id, d.department_name, l.city
   FROM departments d
   LEFT OUTER JOIN employees e ON d.department_id = e.department_id
   left  JOIN locations l ON d.location_id = l.location_id;
SELECT last_name, department_id, department_name, city
  FROM departments d
  JOIN employees e using(department_id) NATURAL  JOIN locations l ;
  SELECT 'Dear Customer ' || last_name || ',' as "dd" FROM employees;

select to_date('January 10 1999','mm dd yyyy') from dual;
SELECT LOWER(TRIM ('H' FROM 'HelloWorld')) FROM dual;