小编new*_*ser的帖子

在数据库中定义外键还是在应用程序的代码部分中定义外键更好？

MySQLUnique Key和Primary KeyMySQL之间的主要区别是什么？

我正在为 Invoice.In 做一个小应用程序，表格将是这样的

=== invoice ===
id (pk)
customer_id (fk)
invoice_title
invoice_issue_date
due_date
description
created_by
updated_by
created_at
updated_at

=== invoice_items ===
id (pk)
invoice_id (fk)
customer_id (fk)
product_name 
unit_cost 
quantity 
apply_tax1 
apply_tax2 
discount 
description 
created_by 
updated_by 
created_at 
updated_at 

=== customers ===
id (pk)
business_email 
business_name 
customer_name 
business_address 
town/city 
state/province 
postalzip_code 
country 
phone 
mob 
fax 
created_by 
updated_by 
created_at 
updated_at 

=== estimates ===
id (pk)
address 
estimate_title 
estimate_no 
purchase_order_no 
estimate_date 
description 
created_by 
updated_by 
created_at 
updated_at 

=== estimate_items ===
id (pk)
estimate_id (fk) …

我有customers. 该customers表是这样的

+------------------+
|     Customers    |
+------------------+
| id  (PK)         |
| business_email   |
| business_name    |
| customer_name    |
| payment_terms    |
| currency         |
| business_address |
| city             |
| state            |
| postal_code      |
| country          |
| phone            |
| created_at       |
| updated_at       |
+------------------+

现在，我希望把送货地址在我的应用程序，客户可以任意提他的航运address.SØ我做了一个额外的表shipping address像这样

+------------------+
| Shipping Address |
+------------------+
| id  (PK)         |
| contact_name     |
| contact_address  |
| delivery_address |
| created_at …