In relational databases, the information schema (information_schema) is an ANSI-standard set of read-only views that provide information about all of the tables, views, columns, and procedures in a database. It can be used as a source of the information that some databases make available through non-standard commands, such as: => 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)

Implementation

As a notable exception among major database systems, Oracle does not implement the information schema. An open-source project exists to address this. RDBMSs that support information_schema include: RDBMSs that do not support information_schema include: