The compatibility of imports is never the type of the data (CSV, EXCEL, SQL tables converted into files) but the compatibility of the data models. 

For example, Odoo has "PARTNER" which is a single abstraction for a Company, Individual, Customer, Vendor, Employee, etc.  Other systems may have multiple abstractions. In order to import Customer and Vendors it might need TWO sql table extracts.

Another example, Odoo has "PRODUCT" and "INVENTORY" which means you can create a product with no inventory (because you haven't bought it yet) but other systems may not make the distinction.  It might need the same table imported TWICE into Odoo - once to create the product - a second time to create the Inventory adjustment that puts a quantity into stock for that product.

YES, you can import SQL tables into Odoo, but the information from those tables might need to go through some sort of transformation process (remove information, consolidate information, join information from other tables) before it can be "cleanly" imported.