mysql - 左连接和右连接是否足够？

Question

假设我有 2 个如下表:

表:产品

-------------
|PRODUCT    |
-------------
|IPAD       |
-------------
|IPHONE     |
-------------

表:销售额

-----------------------------   
SALES_PERSON|PRODUCT|IS_SOLD|
-----------------------------
ALICE       |IPAD   |   1   |
-----------------------------
JOHN        |IPONE  |   1   |
-----------------------------

是否可以让 SQL 语句产生如下结果？

--------------------------------
SALES_PERSON| PRODUCT | IS_SOLD|
--------------------------------
ALICE       | IPAD    | 1      |
--------------------------------
ALICE       | IPHONE  | null   |
--------------------------------
JOHN        | IPAD    | null   |
--------------------------------
JOHN        | IPHONE  | 1      |
--------------------------------

Answer 1

您可以使用联接来执行此操作，但您需要不止一个。您需要在产品和销售人员之间创建交叉产品。左侧将此连接到 sales_person 表:

select pe.sales_person, p.product, sp.is_sold
from product p cross join
     (select distinct sales_person from sales) pe left outer join
     sales_person sp
     on sp.product = p.product and
        sp.sales_person = pe.sales_person;