Magento 数据表结构 EAV模型详解

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:
  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  

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. +----------------+------------------+-------------------+-----------------+-----------------+  

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. +---------------------+----------------+------------------+--------------------+--------------+  

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. +--------------+----------------+------------------+--------------+  

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 | [email protected] |  
  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. +----------+----------------+--------------+-----------+-------------------------------------

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

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