Difference between EAV catalog and Flat catalog is as following:
1. Eav Catalog
EAV is entity attribute value database model, where data is fully in normalized form. Each column data value is stored in their respective data type table. Example, for a product,
product ID is stored in
product name in
product price in
product created date in
product description in
EAV is complex as it joins 5-6 tables even if you want to get just one product’s details.
Columns are called attributes in EAV.
2. Flat Catalog
Flat model uses just one table, so it’s not normalized and uses more database space. It clears the EAV overhead,
It’s good when comes to performance, as it will only require one
query to load whole product instead of joining 5-6 tables to get just
one product’s details.
Columns are called fields in flat model.
Magento implemented indexers which will periodically query the standard collections and populate flat database tables in following format. Where * is store id.
These tables have non-normalized product and category data that’s intended to be read only. This allows Magento to fetch category and product data in a single query.
You can enable flat catalog by navigating to
System > Configuration > Catalog > Frontend > Use Flat Catalog Category | Use Flat Catalog Product. Set this to yes.
If you are adding new attribute in EAV table for catalog. Then don't forget to run re-indexing
(System > Configuration > Index Management). Re-indexing refreshes your flat catalog tables.
Hope you understand