Information Schema

In relational databases, the Information Schema is an ANSI standard set of read-only views which provide information about all of the tables, views, columns, and procedures in a database. It can be used as a source of the information which some databases make available through non-standard commands, such as the SHOW command of MySQL and the DESCRIBE command of Oracle.

=> select count(table_name) from information_schema.tables; count ------- 99 (1 row) => select column_name, data_type, column_default, is_nullable from information_schema.columns where table_name='alpha'; column_name | data_type | column_default | is_nullable -------------+-----------+----------------+------------- foo | integer | | YES bar | character | | YES (2 rows) => select * from information_schema.information_schema_catalog_name; catalog_name -------------- johnd (1 row)

External links

* [http://dev.mysql.com/doc/refman/5.1/en/information-schema.html Information Schema in MySQL]
* [http://www.postgresql.org/docs/current/interactive/information-schema.html Information Schema in Postgresql]
* [http://www.sqlite.org/cvstrac/wiki?p=InformationSchema Information Schema in SQLite]
* [http://msdn.microsoft.com/en-us/library/ms186778.aspx Information Schema in Microsoft SQL Server 2005]