SQL在INNER JOIN时，也可以将子查询加入进来

mysql> SELECT a.account_id, a_cust_id, a.open_date, a.product_cd 
    -> FROM account AS a INNER JOIN
    -> (SELECT emp_id, assigned_branch_id 
    -> FROM employee
    -> WHERE start_date < '20017-01-01'
    -> AND (title = 'Teller' OR title = 'Head Teller')) AS e
    -> ON a.open_emp_id = e.emp_id
    -> INNER JOIN
    -> (SELECT branch_id
    -> FROM branch
    -> WHERE name = 'Woburn Branch') as b
    -> ON e.assigned_branch_id = b.branch_id;