动态自定义字段属性--Magento的EAV模型

EAV ： Entity - Attribute - Value 的缩写，是数据库模型的一种，使用eav建模的好处是可以动态为数据模型增加或移除属性。

1. 问题提出:

假设需要定义一个实体Customer的信息，通常我们只要定义一个表为customer，并定义相应的属性即可。倘若某天需要为customer增加一个新的属性如“毕业学校”，那么就需要更改表的结构。
如果使用EAV模型则不必改变表结构。

2. Magento的EAV模型定义:

在Magento中，EAV模型相关的表定义有：

Java代码 

1. eav_attribute               
2. eav_attribute_group         
3. eav_attribute_option        
4. eav_attribute_option_value  
5. eav_attribute_set           
6. eav_entity                  
7. eav_entity_attribute        
8. eav_entity_datetime         
9. eav_entity_decimal          
10. eav_entity_int              
11. eav_entity_store            
12. eav_entity_text             
13. eav_entity_type             
14. eav_entity_varchar  

eav_attribute             eav_attribute_group       eav_attribute_option      eav_attribute_option_valueeav_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

现在让我来观察最重要的三张表
eav_entity_type，eav_entity_attribute，eav_attribute

1) eav_entity_type表用来定义实体的基本信息。

Sql代码 

1. mysql> select * from  eav_entity_type where entity_type_id=1;  
2. +----------------+------------------+-------------------+-----------------+-----------------+  
3. | entity_type_id | entity_type_code | entity_model      | attribute_model | entity_table    | +----------------+------------------+-------------------+-----------------+-----------------+  
4. |              1 | customer         | customer/customer |                 | customer/entity |  
5. +----------------+------------------+-------------------+-----------------+-----------------+  

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表用来定义实体customer模型包含哪些属性

Sql代码 

1. mysql> select * from eav_entity_attribute  where entity_type_id='1';  
2. +---------------------+----------------+------------------+--------------------+--------------+  
3. | entity_attribute_id | entity_type_id | attribute_set_id | attribute_group_id | attribute_id |  
4. +---------------------+----------------+------------------+--------------------+--------------+  
5. |                   1 |              1 |                1 |                  1 |            1 |  
6. |                   2 |              1 |                1 |                  1 |            2 |  
7. |                   3 |              1 |                1 |                  1 |            3 |  
8. |                   4 |              1 |                1 |                  1 |            4 |  
9. |                   5 |              1 |                1 |                  1 |            5 |  
10. |                   6 |              1 |                1 |                  1 |            6 |  
11. |                   7 |              1 |                1 |                  1 |            7 |  
12. |                   8 |              1 |                1 |                  1 |            8 |  
13. |                   9 |              1 |                1 |                  1 |            9 |  
14. |                  10 |              1 |                1 |                  1 |           10 |  
15. |                  11 |              1 |                1 |                  1 |           11 |  
16. |                  12 |              1 |                1 |                  1 |           12 |  
17. |                  13 |              1 |                1 |                  1 |           13 |  
18. |                  14 |              1 |                1 |                  1 |           14 |  
19. |                  15 |              1 |                1 |                  1 |           15 |  
20. |                  16 |              1 |                1 |                  1 |           16 |  
21. +---------------------+----------------+------------------+--------------------+--------------+  

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实体包含16个属性，下面的语句查看每个属性的具体定义

Sql代码 

1. mysql> select * from eav_attribute where attribute_id<=16 and attribute_id>=1 ;  
2. +--------------+----------------+------------------+--------------+  
3. | attribute_id | entity_type_id | attribute_code   | backend_type |  
4. +--------------+----------------+------------------+--------------+  
5. |            1 |              1 | website_id       | static       |  
6. |            2 |              1 | store_id         | static       |  
7. |            3 |              1 | created_in       | varchar      |  
8. |            4 |              1 | prefix           | varchar      |  
9. |            5 |              1 | firstname        | varchar      |  
10. |            6 |              1 | middlename       | varchar      |  
11. |            7 |              1 | lastname         | varchar      |  
12. |            8 |              1 | suffix           | varchar      |  
13. |            9 |              1 | email            | static       |  
14. |           10 |              1 | group_id         | static       |  
15. |           11 |              1 | dob              | datetime     |  
16. |           12 |              1 | password_hash    | varchar      |  
17. |           13 |              1 | default_billing  | int          |  
18. |           14 |              1 | default_shipping | int          |  
19. |           15 |              1 | taxvat           | varchar      |  
20. |           16 |              1 | confirmation     | varchar      |  
21. +--------------+----------------+------------------+--------------+  

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属性定义的添加和删除，只需要增加或删除 eav_entity_attribute的记录即可

3. 使用EAV模型
现在，在Magento系统注册一个新的用户，看看实例数据如何存放在数据库

Sql代码 

1. mysql> select * from customer_entity            ;  
2. +-----------+----------------+------------------+------------+--------------------+  
3. | entity_id | entity_type_id | attribute_set_id | website_id | email              |  
4. +-----------+----------------+------------------+------------+--------------------+  
5. |         1 |              1 |                0 |          1 | [e-mail] |  
6. +-----------+----------------+------------------+------------+--------------------+  
7.   
8. mysql> select * from customer_entity_varchar    ;  
9. +----------+----------------+--------------+-----------+-------------------------------------+  
10. | value_id | entity_type_id | attribute_id | entity_id | value                               |  
11. +----------+----------------+--------------+-----------+-------------------------------------+  
12. |        1 |              1 |            5 |         1 | Koda                                |  
13. |        2 |              1 |            7 |         1 | Guo                                 |  
14. |        4 |              1 |            3 |         1 | Default Store View                  |  
15. |        5 |              1 |           12 |         1 | 2256e441b74ab3454a41c821f5de1e9d:9s |  
16. +----------+----------------+--------------+-----------+-------------------------------------+  

mysql> select * from customer_entity            ;+-----------+----------------+------------------+------------+--------------------+| entity_id | entity_type_id | attribute_set_id | website_id | email              |+-----------+----------------+------------------+------------+--------------------+|         1 |              1 |                0 |          1 | [e-mail] |+-----------+----------------+------------------+------------+--------------------+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 |+----------+----------------+--------------+-----------+-------------------------------------+

从上表看到customer_entity 和customer_entity_varchar用来存放相应属性的实际输入值。如：
Koda, Guo分别属性编号5,7即firstname和lastname实际值

和customer实体定义相对应的实例存放的相关表包括：

Java代码 

1. customer_entity            
2. customer_entity_datetime   
3. customer_entity_decimal    
4. customer_entity_int        
5. customer_entity_text       
6. customer_entity_varchar    

customer_entity          customer_entity_datetime customer_entity_decimal  customer_entity_int      customer_entity_text     customer_entity_varchar  

总结
了解Magento的EAV模型结构是扩展Magento必须的知识。 其意义在于，我们常常需要扩展Magento某些实体的属性，或者创建自定义的eav模型实例。希望本文对你有所启示。