1. 問題提出:
假設需要定義一個實體Customer的信息，通常我們只要定義一個表爲customer，並定義相應的屬性即可。倘若某天需要爲customer增加一個新的屬性如“畢業學校”，那麼就需要更改表的結構。
如果使用EAV模型則不必改變表結構。
2. Magento的EAV模型定義:
在Magento中，EAV模型相關的表定義有：
- eav_attribute
- eav_attribute_group
- eav_attribute_option
- eav_attribute_option_value
- eav_attribute_set
- eav_entity
- eav_entity_attribute
- eav_entity_datetime
- eav_entity_decimal
- eav_entity_int
- eav_entity_store
- eav_entity_text
- eav_entity_type
- eav_entity_varchar
eav_attribute
eav_attribute_group
eav_attribute_option
eav_attribute_option_value
eav_attribute_set
eav_entity
eav_entity_attribute
eav_entity_datetime
eav_entity_decimal
eav_entity_int
eav_entity_store
eav_entity_text
eav_entity_type
eav_entity_varchar現在讓我來觀察最重要的三張表
eav_entity_type，eav_entity_attribute，eav_attribute
1) eav_entity_type表用來定義實體的基本信息。
- mysql> select * from eav_entity_type where entity_type_id=1;
- +----------------+------------------+-------------------+-----------------+-----------------+
- | entity_type_id | entity_type_code | entity_model | attribute_model | entity_table | +----------------+------------------+-------------------+-----------------+-----------------+
- | 1 | customer | customer/customer | | customer/entity |
- +----------------+------------------+-------------------+-----------------+-----------------+
mysql> select * from eav_entity_type where entity_type_id=1;
+----------------+------------------+-------------------+-----------------+-----------------+
| entity_type_id | entity_type_code | entity_model | attribute_model | entity_table | +----------------+------------------+-------------------+-----------------+-----------------+
| 1 | customer | customer/customer | | customer/entity |
+----------------+------------------+-------------------+-----------------+-----------------+
2). eav_entity_attribute表用來定義實體customer模型包含哪些屬性
- mysql> select * from eav_entity_attribute where entity_type_id='1';
- +---------------------+----------------+------------------+--------------------+--------------+
- | entity_attribute_id | entity_type_id | attribute_set_id | attribute_group_id | attribute_id |
- +---------------------+----------------+------------------+--------------------+--------------+
- | 1 | 1 | 1 | 1 | 1 |
- | 2 | 1 | 1 | 1 | 2 |
- | 3 | 1 | 1 | 1 | 3 |
- | 4 | 1 | 1 | 1 | 4 |
- | 5 | 1 | 1 | 1 | 5 |
- | 6 | 1 | 1 | 1 | 6 |
- | 7 | 1 | 1 | 1 | 7 |
- | 8 | 1 | 1 | 1 | 8 |
- | 9 | 1 | 1 | 1 | 9 |
- | 10 | 1 | 1 | 1 | 10 |
- | 11 | 1 | 1 | 1 | 11 |
- | 12 | 1 | 1 | 1 | 12 |
- | 13 | 1 | 1 | 1 | 13 |
- | 14 | 1 | 1 | 1 | 14 |
- | 15 | 1 | 1 | 1 | 15 |
- | 16 | 1 | 1 | 1 | 16 |
- +---------------------+----------------+------------------+--------------------+--------------+
mysql> select * from eav_entity_attribute where entity_type_id='1';
+---------------------+----------------+------------------+--------------------+--------------+
| entity_attribute_id | entity_type_id | attribute_set_id | attribute_group_id | attribute_id |
+---------------------+----------------+------------------+--------------------+--------------+
| 1 | 1 | 1 | 1 | 1 |
| 2 | 1 | 1 | 1 | 2 |
| 3 | 1 | 1 | 1 | 3 |
| 4 | 1 | 1 | 1 | 4 |
| 5 | 1 | 1 | 1 | 5 |
| 6 | 1 | 1 | 1 | 6 |
| 7 | 1 | 1 | 1 | 7 |
| 8 | 1 | 1 | 1 | 8 |
| 9 | 1 | 1 | 1 | 9 |
| 10 | 1 | 1 | 1 | 10 |
| 11 | 1 | 1 | 1 | 11 |
| 12 | 1 | 1 | 1 | 12 |
| 13 | 1 | 1 | 1 | 13 |
| 14 | 1 | 1 | 1 | 14 |
| 15 | 1 | 1 | 1 | 15 |
| 16 | 1 | 1 | 1 | 16 |
+---------------------+----------------+------------------+--------------------+--------------+
3), 由上表推出customer實體包含16個屬性，下面的語句查看每個屬性的具體定義
- mysql> select * from eav_attribute where attribute_id<=16 and attribute_id>=1 ;
- +--------------+----------------+------------------+--------------+
- | attribute_id | entity_type_id | attribute_code | backend_type |
- +--------------+----------------+------------------+--------------+
- | 1 | 1 | website_id | static |
- | 2 | 1 | store_id | static |
- | 3 | 1 | created_in | varchar |
- | 4 | 1 | prefix | varchar |
- | 5 | 1 | firstname | varchar |
- | 6 | 1 | middlename | varchar |
- | 7 | 1 | lastname | varchar |
- | 8 | 1 | suffix | varchar |
- | 9 | 1 | email | static |
- | 10 | 1 | group_id | static |
- | 11 | 1 | dob | datetime |
- | 12 | 1 | password_hash | varchar |
- | 13 | 1 | default_billing | int |
- | 14 | 1 | default_shipping | int |
- | 15 | 1 | taxvat | varchar |
- | 16 | 1 | confirmation | varchar |
- +--------------+----------------+------------------+--------------+
mysql> select * from eav_attribute where attribute_id<=16 and attribute_id>=1 ;
+--------------+----------------+------------------+--------------+
| attribute_id | entity_type_id | attribute_code | backend_type |
+--------------+----------------+------------------+--------------+
| 1 | 1 | website_id | static |
| 2 | 1 | store_id | static |
| 3 | 1 | created_in | varchar |
| 4 | 1 | prefix | varchar |
| 5 | 1 | firstname | varchar |
| 6 | 1 | middlename | varchar |
| 7 | 1 | lastname | varchar |
| 8 | 1 | suffix | varchar |
| 9 | 1 | email | static |
| 10 | 1 | group_id | static |
| 11 | 1 | dob | datetime |
| 12 | 1 | password_hash | varchar |
| 13 | 1 | default_billing | int |
| 14 | 1 | default_shipping | int |
| 15 | 1 | taxvat | varchar |
| 16 | 1 | confirmation | varchar |
+--------------+----------------+------------------+--------------+
所以，使用上述的模型，一旦有CUSTOMER屬性定義的添加和刪除，只需要增加或刪除 eav_entity_attribute的記錄即可
3. 使用EAV模型
現在，在Magento系統註冊一個新的用戶，看看實例數據如何存放在數據庫
- mysql> select * from customer_entity ;
- +-----------+----------------+------------------+------------+--------------------+
- | entity_id | entity_type_id | attribute_set_id | website_id | email |
- +-----------+----------------+------------------+------------+--------------------+
- | 1 | 1 | 0 | 1 | [email protected] |
- +-----------+----------------+------------------+------------+--------------------+
- mysql> select * from customer_entity_varchar ;
- +----------+----------------+--------------+-----------+-------------------------------------+
- | value_id | entity_type_id | attribute_id | entity_id | value |
- +----------+----------------+--------------+-----------+-------------------------------------+
- | 1 | 1 | 5 | 1 | Koda |
- | 2 | 1 | 7 | 1 | Guo |
- | 4 | 1 | 3 | 1 | Default Store View |
- | 5 | 1 | 12 | 1 | 2256e441b74ab3454a41c821f5de1e9d:9s |
- +----------+----------------+--------------+-----------+-------------------------------------+
mysql> select * from customer_entity ;
+-----------+----------------+------------------+------------+--------------------+
| entity_id | entity_type_id | attribute_set_id | website_id | email |
+-----------+----------------+------------------+------------+--------------------+
| 1 | 1 | 0 | 1 | [email protected] |
+-----------+----------------+------------------+------------+--------------------+
mysql> select * from customer_entity_varchar ;
+----------+----------------+--------------+-----------+-------------------------------------+
| value_id | entity_type_id | attribute_id | entity_id | value |
+----------+----------------+--------------+-----------+-------------------------------------+
| 1 | 1 | 5 | 1 | Koda |
| 2 | 1 | 7 | 1 | Guo |
| 4 | 1 | 3 | 1 | Default Store View |
| 5 | 1 | 12 | 1 | 2256e441b74ab3454a41c821f5de1e9d:9s |
+----------+----------------+--------------+-----------+-------------------------------------+
從上表看到customer_entity 和customer_entity_varchar用來存放相應屬性的實際輸入值。如：
Koda, Guo分別屬性編號5,7即firstname和lastname實際值
和customer實體定義相對應的實例存放的相關表包括：
- customer_entity
- customer_entity_datetime
- customer_entity_decimal
- customer_entity_int
- customer_entity_text
- customer_entity_varchar
customer_entity
customer_entity_datetime
customer_entity_decimal
customer_entity_int
customer_entity_text
customer_entity_varchar
總結
瞭解Magento的EAV模型結構是擴展Magento必須的知識。 其意義在於，我們常常需要擴展Magento某些實體的屬性，或者創建自定義的eav模型實例。希望本文對你有所啓示。