Information schema

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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. [1] It can be used as a source of the information that some databases make available through non-standard commands, such as:

Contents

 => 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 as of 2015 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:

See also

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References

  1. Melton, Jim; Simon, Alan R. (1993). "19.2 Metadata, Repositories and The INFORMATION_SCHEMA". Understanding the New SQL: A Complete Guide . The Morgan Kaufmann series in data management systems, ISSN 1046-1698. Morgan Kaufmann. p.  371. ISBN   9781558602458 . Retrieved 2015-10-22. Metadata that applies primarily to the runtime database environment is managed through the INFORMATION_SCHEMA. [...] Metadata that applies to the information system environment as a whole is managed through the dictionary or repository.
  2. "Snowflake Information Schema". www.snowflake.com. Retrieved 2024-03-25.
  3. "Pragma statements supported by SQLite". www.sqlite.org. Retrieved 2022-02-01.