ROWID Datatype Each row in the database has an address. You can examine a row's address by querying the pseudocolumn ROWID. Values of this pseudocolumn are hexadecimal strings representing the address of each row. These strings have the datatype ROWID. For more information on the ROWID pseudocolumn, see "Pseudocolumns". You can also create tables and clusters that contain actual columns having the ROWID datatype. Oracle does not guarantee that the values of such columns are valid ROWIDs.
Each row in the database has an address. You can examine a row's address by querying the pseudocolumn ROWID. Values of this pseudocolumn are hexadecimal strings representing the address of each row. These strings have the datatype ROWID. For more information on the ROWID pseudocolumn, see "Pseudocolumns". You can also create tables and clusters that contain actual columns having the ROWID datatype. Oracle does not guarantee that the values of such columns are valid ROWIDs.
user_tables是系统视图，是没有rowid的。
但视图没有，所以user_tables没有呀