Slide 5.8: Oracle data dictionary

Oracle Data Dictionary

Oracle data dictionary contains all information about the structures and objects of the database such as tables, columns, users, data files, etc. The data stored in the data dictionary are also called metadata. Although data dictionary is usually the domain of database administrators (DBAs), it is a valuable source of information for end users and developers.

Data Dictionary Tables
Tables and views provided by data dictionary contain information about

users and their privileges,
tables, table columns and their data types, integrity constraints, indexes,
statistics about tables and indexes used by the optimizer,
privileges granted on database objects, and
storage structures of the database.

The SQL command

   SELECT * FROM dict[ionary];

lists all tables and views of the data dictionary that are accessible to the users. The selected information includes the name and a short description of each table and view. Before issuing this query, check the column definitions of DICT[IONARY] using “desc DICT[IONARY]” and set the appropriate values for column using the format command. The query

   SELECT * FROM tab;

retrieves the names of all tables owned by the user who issues this command. The query

   SELECT * FROM col;

returns all information about the columns of one’s own tables.

Review: Oracle Data Dictionary

DESC user_tables;

SELECT * FROM dictionary;

SELECT * FROM tab;

SELECT table_name FROM all_tables;

Result: