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

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

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

mysql>select*fromeav_entity_typewhereentity_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表用来定义实体customer模型包含哪些属性

Sql代码

mysql>select*fromeav_entity_attributewhereentity_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

mysql>select*fromeav_attributewhereattribute_id<=16andattribute_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

mysql>select*fromcustomer_entity            ;

+-----------+----------------+------------------+------------+--------------------+

| entity_id | entity_type_id | attribute_set_id | website_id | email              |

+-----------+----------------+------------------+------------+--------------------+

|         1 |              1 |                0 |          1 | koda.guo@gmail.com |

+-----------+----------------+------------------+------------+--------------------+

mysql> select*fromcustomer_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 | DefaultStoreView|

|        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 | koda.guo@gmail.com |

+-----------+----------------+------------------+------------+--------------------+

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

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

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。