Cosmos DB: It’s Globally distributed and scalable horizontally and we can integrate the MongoDB api, DOCUMENT DB API, Graph API etc. Azure cosmos database is no SQL database as SERVICES which is designed to help elasticity and flexibility. We can use it in IOT and global-facing application in a cloud-based application.
SQL DB: It’s Database as services and has relation DBMS. It’s a TRADITIONAL SQL database SERVER which we can use a database as services for cloud-based applications, we can integrate with API like OLE Db, Tabular systems, ado.net etc. It provides compatibility with on-premise SQL Database.