Hi Rubane,
Use this Select statement:
select P."ProductId" , "Category","NameId", P."Currency", "GrossAmount", "Quantity" FROM "SAP_HANA_EPM_DEMO"."sap.hana.democontent.epm.data::products" AS P , "SAP_HANA_EPM_DEMO"."sap.hana.democontent.epm.data::purchaseOrderItem" AS B where P. "ProductId" = B."ProductId";
The issue is due to case sensitivity and the . or : coming in the name. You have to use " ". And also you have missed mentioning the schema name.
Starting with, try with simple SQL in SQL editor as mentioned by Fernando
Regards,
Krishna Tangudu