Oracle Data Dictionary (Cont.)

Data Dictionary Views
The views provided by data dictionary are divided into three groups: USER, ALL, and DBA. The group builds the prefix for each view name.
USER_
Tuples in the USER views contain information about objects owned by the account performing the SQL query (current user).

View Description
USER_TABLES All tables with their name, number of columns, storage information, statistical information etc. (TABS)
USER_CATALOG Tables, views, and synonyms (CAT)
USER_COL_COMMENTS Comments on columns
USER_CONSTRAINTS Constraint definitions for tables
USER_INDEXES All information about indexes created for tables (IND)
USER_OBJECTS All database objects owned by the user (OBJ)
USER_TAB_COLUMNS Columns of the tables and views owned by the user (COLS)
USER_TAB_COMMENTS Comments on tables and views
USER_TRIGGERS Triggers defined by the user
USER_USERS Information about the current user
USER_VIEWS Views defined by the user

For example, to list the column definitions of USER_TABLES: 
   SQL> DESC user_tables; 
   Name               Null?     Type
   -----------------  --------  ---------------------
   TABLE_NAME         NOT NULL  VARCHAR2(30)
   ...
and the following command lists the tables owned by the user: 
   SQL> SELECT table_name FROM user_tables; 
   TABLE_NAME                     
   ------------------------ 
   CUSTOMERS
   GAMES



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