magento EAV数据库Magento EAV structure & role of eav_attribute’s backend_type field
Introduction:
Magento database is based on EAV(Entity Attribute Value) architecture. And it uses this architecture especially for categories, products, customers & customer addresses.
Before Magento version 1.4.x it used EAV structure for orders as well but thereafter order’s eav structure has been converted to flat structure.
From the defination of EAV:
Entity(E):
Entity actually refers to data item.
In Magento:
catalog_category_entity catalog_product_entity customer_entity customer_address_entity
are the entity tables for categories, products, customers & customer addresses respectively.
Attribute(A):
Attribute refers to the different attributes of an Entity.
In Magento, attributes related to an entity are stored in a single table: eav_attribute but differentiated by field: entity_type_id.
We can easily find all the attributes related to an entity using the following SQL query(For Example: product):
SELECT
attribute_code,
attribute_id,
backend_type
FROM
eav_attribute
WHERE entity_type_id =
(SELECT
entity_type_id
FROM
eav_entity_type
WHERE entity_type_code = 'catalog_product')
Which gives the following results:
+----------------------------+--------------+--------------+ | attribute_code | attribute_id | backend_type | +----------------------------+--------------+--------------+ | activation_information | 496 | text | | color | 272 | int | | color_code | 950 | varchar | | computer_manufacturers | 510 | int | | contrast_ratio | 875 | int | | cost | 100 | decimal | | country_orgin | 507 | text | | cpu_speed | 877 | int | | created_at | 930 | static | | custom_design | 571 | varchar | | custom_design_from | 572 | datetime | | custom_design_to | 573 | datetime | | custom_layout_update | 531 | text | | description | 97 | text | | dimension | 494 | text | | enable_googlecheckout | 903 | int | | finish | 509 | text | | gallery | 271 | varchar | | gender | 501 | int | | gift_message_available | 562 | varchar | | harddrive_speed | 878 | varchar | | hardrive | 499 | text | | has_options | 838 | static | | image | 106 | varchar | | image_label | 879 | varchar | | in_depth | 492 | text | | is_imported | 949 | int | | is_recurring | 933 | int | | links_exist | 947 | int | | links_purchased_separately | 904 | int | | links_title | 906 | varchar | | manufacturer | 102 | int | | max_resolution | 873 | varchar | | media_gallery | 703 | varchar | | megapixels | 513 | int | | memory | 498 | text | | meta_description | 105 | varchar | | meta_keyword | 104 | text | | meta_title | 103 | varchar | | minimal_price | 503 | decimal | | model | 495 | text | | name | 96 | varchar | | news_from_date | 704 | datetime | | news_to_date | 705 | datetime | | old_id | 110 | int | | options_container | 836 | varchar | | package_id | 951 | int | | page_layout | 929 | varchar | | price | 99 | decimal | | price_type | 859 | int | | price_view | 862 | int | | processor | 497 | text | | ram_size | 874 | varchar | | recurring_profile | 934 | text | | required_options | 837 | static | | response_time | 876 | varchar | | room | 508 | int | | samples_title | 905 | varchar | | screensize | 500 | text | | shape | 476 | text | | shipment_type | 863 | int | | shipping_qty | 952 | int | | shirt_size | 525 | int | | shoe_size | 502 | int | | shoe_type | 107 | int | | short_description | 506 | text | | sku | 98 | static | | sku_type | 860 | int | | small_image | 109 | varchar | | small_image_label | 880 | varchar | | special_from_date | 568 | datetime | | special_price | 567 | decimal | | special_to_date | 569 | datetime | | status | 273 | int | | tax_class_id | 274 | int | | thumbnail | 493 | varchar | | thumbnail_label | 881 | varchar | | tier_price | 270 | decimal | | updated_at | 931 | static | | url_key | 481 | varchar | | url_path | 570 | varchar | | visibility | 526 | int | | weight | 101 | decimal | | weight_type | 861 | int | +----------------------------+--------------+--------------+
Similarly you can find attributes for other entities just by using following values for entity_type_code:
catalog_category customer customer_address
or categories, customers & customer address respectively.
Note: You can get the related values for entity_type_code from table: eav_entity_type.
Value(V):
Value refers to the actual value of the attribute of the entity.
In Magento attribute values of an entity (for example: product) are stored in catalog_product_entity_[backend_type] tables.
Where [backend_type] refers to the value of field: backend_type (except value ‘static’) of table: eav_attribute.
Following SQL is used to find all the backend types related to a product entity:
SELECT DISTINCT
backend_type
FROM
eav_attribute
WHERE entity_type_id =
(SELECT
entity_type_id
FROM
eav_entity_type
WHERE entity_type_code = 'catalog_product')
Which results:
+--------------+ | backend_type | +--------------+ | text | | int | | varchar | | decimal | | static | | datetime | +--------------+
So tables:
catalog_product_entity_text catalog_product_entity_int catalog_product_entity_varchar catalog_product_entity_decimal catalog_product_entity_datetime
are used for storing values for an attributes of related backend_type.
Note: You must be wondering about backend_type = static. For an attribute with the static backend_type, values are stored as a column directly in the entity table. For example: sku is an attribute of backend_type = static and it’s values are stored in the entity table itself: catalog_product_entity under field: sku.
That’s all about the definition of EAV relating to Magento.
Hopefully now you are able to differentiate which attribute values goes where (in which table) based on the backend_type.
Thanks for reading & Happy E-Commerce!!
来源：http://www.blog.magepsycho.com/magento-eav-structure-role-of-eav_attributes-backend_type-field/