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Information schema

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Title: Information schema  
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Subject: Databases, From (SQL), Non-Relational Databases, Metadata, MySQL
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Information schema

In relational databases, the information schema (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.[1] It can be used as a source of the information which 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)

Contents

  • Implementation 1
  • See also 2
  • External links 3
  • References 4

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 which support information_schema include:

  • Microsoft SQL Server
  • MySQL
  • PostgreSQL

RDBMSs which do not support information_schema include:

  • Oracle Database
  • IBM DB2
  • SQLite

See also

External links

  • Information schema in MySQL 5.7
  • Information schema in PostgreSQL (current version)
  • Information schema in SQLite
  • Information schema in Microsoft SQL Server 2014
  • Information schema in Microsoft SQL Server Compact 4.0
  • Oracle Information Schema project on sourceforge

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.  


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