You are posting into the wrong forum since this one is just for Oracle's SQL Developer tool.
Having that said,
you should *never* create any object in the sys schema! The user sys is the owner of all data dictionary objects and is treated special in many ways.
Always create a new user to play around with. Creating new users also should not be done the a login as sys. In fact the only reason for logging in as sys is starting or stopping the database. A predefined DBA user that can be used to create your own users is SYSTEM.
Hope that helps,
This forum is ONLY for Sql Developer questions.
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If you still need help after reading the other responder's reply repost your question in the General Database forum