Re: in the different schema ，the sequence name is same， and a table's column definition use this sequence,so，how can I identify sequence's schema name by system view/table:

Since you didn’t schema qualify the sequence name every single time a default value is created the sequence will be looked up anew.  The stored expression is not associated with any specific object.

This is also why there is a separate step to mark a sequence as being owned by a table.  That establishes a dependency that this textual form is unable to do.

David J.