You specify the main URL as the online search engine could have trouble identifying which one particular need to be the principal URL.  The next tutorial will tell you about the best way to enable Canonical URLs in Prestashop 1.5. The presented SQL scripts demonstrate how to incorporate columns https://addons.prestashop.com/es/seo-posicionamiento-buscadores/31857-google-rich-snippets-automatico-json-ld-opengraph-seo.html