I created an edge without attribute and guess what? it was created but still can not query it but then i created the same edge again and now they both are having same rid>?
I suggest you to start using OrientDB from the tutorial. This is an extract:
Starting from OrientDB v1.4.x edges, by default, are managed as lightweight edges: they don't have own identities as record, but are physically stored as links inside vertices. OrientDB automatically uses Lightweight edges only when edges have no properties, otherwise regular edges are used. From the logic point of view, lightweight edges are edges at all the effects, so all the graph functions work correctly. This is to improve performance and reduce the space on disk. But as a consequence, since lightweight edges don't exist as separate records in the database, the following query will not return the lightweight edges:
SELECT FROM E
In most of the cases Edges are used from Vertices, so this doesn't cause any particular problem. In case you need to query Edges directly, even those with no properties, disable lightweight edge feature by executing this command once:
ALTER DATABASE CUSTOM useLightweightEdges=false
This will only take effect for new edges. For more information look at Troubleshooting.