By default, product recommendations uniquely identify your products by combining two fields: the product name and the SKU. In most cases, this is a reliable default configuration, as it makes sure product recommendations work even if you don't have a unique SKU for every product.
Change the unique product identifier for products in a catalog
Go to Content > Products > Catalogs.
Select Properties for the catalog you want to edit.
From the side panel, under the heading Product recommendation settings, expand the Unique product identifier drop-down menu, then choose the configuration option you want to use
Understand the configuration options
The field options available show what is typically available in both your catalog and order data, so we can reliably link both these data sets together.
Unique product identifier
Name + SKU (default)
Best for most cases. Flexible with imperfect product data, such as missing or duplicate SKUs.
Works if all products have a unique SKU. This setting is more restrictive but does allow for flexibility, such as changing product names and maintaining their link to their orders.
If no SKU is present and product names are the only possible identifier.