前言

• 經過前幾篇瞭解一些基本的指令後，我們可以再為北風資料庫的查詢加入更多的變化

員工city跟country跟客戶資料表裡面有一樣的列表出來

MariaDB [northwind]> 
MariaDB [northwind]> select employeeid, lastname,city , country
    -> from employees
    -> where row(city,country) in
    -> (select city,country from customers);
+------------+-----------+----------+---------+
| employeeid | lastname  | city     | country |
+------------+-----------+----------+---------+
|          1 | Davolio   | Seattle  | USA     |
|          3 | Leverling | Kirkland | USA     |
|          5 | Buchanan  | London   | UK      |
|          6 | Suyama    | London   | UK      |
|          7 | King      | London   | UK      |
|          8 | Callahan  | Seattle  | USA     |
|          9 | Dodsworth | London   | UK      |
+------------+-----------+----------+---------+
7 rows in set (0.075 sec)