The system tables CAT and DUAL are implemented in order to provide Oracle-related functionality. The tables are placed in the system schema SYS.
The system schemas SYS and EXA_STATISTICS are automatically integrated into the namespace. This means that the tables in the system schemas can be accessed without specifying the schema as long as the same table name is not in use in the current schema.
CAT
This system table lists all of the tables and views in the current schema that the current user can access.
CAT is not completely compatible with Oracle, since in Oracle this system table contains only objects that are owned by the user.
All users have access.
| Column | Meaning |
|---|---|
TABLE_NAME
|
Name of the table or the view |
TABLE_TYPE
|
Type of object: TABLE or VIEW |
DUAL
Along the lines of Oracle's identically named system table, this system table can be used to output static information
(for example,. SELECT CURRENT_USER FROM DUAL). It contains one row with one single column.
All users have access.
| Column | Meaning |
|---|---|
DUMMY
|
Contains a NULL value |
