Thanks for reply tungCEO, I'll explain all that I tried. Initially I checked for constraints using following query:
select TABLE_NAME t, COLUMN_NAME c from information_schema.KEY_COLUMN_USAGE
where TABLE_SCHEMA = "dbname"
and REFERENCED_TABLE_NAME = "ps_product"
and REFERENCED_COLUMN_NAME = "id_product" group by t, c
It returns 0 results. Because for some reason prestashop, at least in my case, did not define any constraints. Then I downloaded the er scheme, open on mysql workbench and I can see a lot of arrow representing relations. So I exported model to sql and import in a new empty database. This operation generate some errors but database is created and there are some constraints but I don't think that they are all.
Launching the previous query I get just 29 results and I can't see some obvious foreign key and table name such as id_product_1 and id_product_2 for ps_accessory table. I don't think that it's possible to get all information needed in less then a week reading manually all tables from database schema.
And from my last try I don't think that database schema is free from errors or omissions