How can I create the data table schema and table relationships
Data in Domo doesn't reside in a RDBMS system. So you can't create an ERD like you would in other SQL environments.
THere is a Governance dataset that will give you schemas, https://knowledge.domo.com/Connect/Connecting_to_Data_with_Connectors/Configuring_Each_Connector/Connectors_for_Analytics/Domo_Governance_Datasets_Connector
