How insert data and how to use previous data?

Users Dgraph
2

First in your application you query for the user:

{
some(func: eq(name, "juanbits") ) {
   uid
  }
}

get it’s UID and then create your mutation:

{ 
 set { 
   _:dg <name> "Neo4j" . 
   <${MY_UID}> <use> _:dg . 
   } 
}

also you can check for https://docs.dgraph.io/howto/#upserts