<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 37. The Information Schema</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="ecpg-develop.html" title="36.16. Internals" /><link rel="next" href="infoschema-schema.html" title="37.1. The Schema" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Chapter 37. The Information Schema</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="ecpg-develop.html" title="36.16. Internals">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="client-interfaces.html" title="Part IV. Client Interfaces">Up</a></td><th width="60%" align="center">Part IV. Client Interfaces</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="infoschema-schema.html" title="37.1. The Schema">Next</a></td></tr></table><hr></hr></div><div class="chapter" id="INFORMATION-SCHEMA"><div class="titlepage"><div><div><h2 class="title">Chapter 37. The Information Schema</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="infoschema-schema.html">37.1. The Schema</a></span></dt><dt><span class="sect1"><a href="infoschema-datatypes.html">37.2. Data Types</a></span></dt><dt><span class="sect1"><a href="infoschema-information-schema-catalog-name.html">37.3. <code class="literal">information_schema_catalog_name</code></a></span></dt><dt><span class="sect1"><a href="infoschema-administrable-role-authorizations.html">37.4. <code class="literal">administrable_role_authorizations</code></a></span></dt><dt><span class="sect1"><a href="infoschema-applicable-roles.html">37.5. <code class="literal">applicable_roles</code></a></span></dt><dt><span class="sect1"><a href="infoschema-attributes.html">37.6. <code class="literal">attributes</code></a></span></dt><dt><span class="sect1"><a href="infoschema-character-sets.html">37.7. <code class="literal">character_sets</code></a></span></dt><dt><span class="sect1"><a href="infoschema-check-constraint-routine-usage.html">37.8. <code class="literal">check_constraint_routine_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-check-constraints.html">37.9. <code class="literal">check_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-collations.html">37.10. <code class="literal">collations</code></a></span></dt><dt><span class="sect1"><a href="infoschema-collation-character-set-applicab.html">37.11. <code class="literal">collation_character_set_applicability</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-domain-usage.html">37.12. <code class="literal">column_domain_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-options.html">37.13. <code class="literal">column_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-privileges.html">37.14. <code class="literal">column_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-udt-usage.html">37.15. <code class="literal">column_udt_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-columns.html">37.16. <code class="literal">columns</code></a></span></dt><dt><span class="sect1"><a href="infoschema-constraint-column-usage.html">37.17. <code class="literal">constraint_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-constraint-table-usage.html">37.18. <code class="literal">constraint_table_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-data-type-privileges.html">37.19. <code class="literal">data_type_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-domain-constraints.html">37.20. <code class="literal">domain_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-domain-udt-usage.html">37.21. <code class="literal">domain_udt_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-domains.html">37.22. <code class="literal">domains</code></a></span></dt><dt><span class="sect1"><a href="infoschema-element-types.html">37.23. <code class="literal">element_types</code></a></span></dt><dt><span class="sect1"><a href="infoschema-enabled-roles.html">37.24. <code class="literal">enabled_roles</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-data-wrapper-options.html">37.25. <code class="literal">foreign_data_wrapper_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-data-wrappers.html">37.26. <code class="literal">foreign_data_wrappers</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-server-options.html">37.27. <code class="literal">foreign_server_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-servers.html">37.28. <code class="literal">foreign_servers</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-table-options.html">37.29. <code class="literal">foreign_table_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-tables.html">37.30. <code class="literal">foreign_tables</code></a></span></dt><dt><span class="sect1"><a href="infoschema-key-column-usage.html">37.31. <code class="literal">key_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-parameters.html">37.32. <code class="literal">parameters</code></a></span></dt><dt><span class="sect1"><a href="infoschema-referential-constraints.html">37.33. <code class="literal">referential_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-column-grants.html">37.34. <code class="literal">role_column_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-routine-grants.html">37.35. <code class="literal">role_routine_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-table-grants.html">37.36. <code class="literal">role_table_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-udt-grants.html">37.37. <code class="literal">role_udt_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-usage-grants.html">37.38. <code class="literal">role_usage_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routine-privileges.html">37.39. <code class="literal">routine_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routines.html">37.40. <code class="literal">routines</code></a></span></dt><dt><span class="sect1"><a href="infoschema-schemata.html">37.41. <code class="literal">schemata</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sequences.html">37.42. <code class="literal">sequences</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-features.html">37.43. <code class="literal">sql_features</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-implementation-info.html">37.44. <code class="literal">sql_implementation_info</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-languages.html">37.45. <code class="literal">sql_languages</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-packages.html">37.46. <code class="literal">sql_packages</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-parts.html">37.47. <code class="literal">sql_parts</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-sizing.html">37.48. <code class="literal">sql_sizing</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-sizing-profiles.html">37.49. <code class="literal">sql_sizing_profiles</code></a></span></dt><dt><span class="sect1"><a href="infoschema-table-constraints.html">37.50. <code class="literal">table_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-table-privileges.html">37.51. <code class="literal">table_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-tables.html">37.52. <code class="literal">tables</code></a></span></dt><dt><span class="sect1"><a href="infoschema-transforms.html">37.53. <code class="literal">transforms</code></a></span></dt><dt><span class="sect1"><a href="infoschema-triggered-update-columns.html">37.54. <code class="literal">triggered_update_columns</code></a></span></dt><dt><span class="sect1"><a href="infoschema-triggers.html">37.55. <code class="literal">triggers</code></a></span></dt><dt><span class="sect1"><a href="infoschema-udt-privileges.html">37.56. <code class="literal">udt_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-usage-privileges.html">37.57. <code class="literal">usage_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-user-defined-types.html">37.58. <code class="literal">user_defined_types</code></a></span></dt><dt><span class="sect1"><a href="infoschema-user-mapping-options.html">37.59. <code class="literal">user_mapping_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-user-mappings.html">37.60. <code class="literal">user_mappings</code></a></span></dt><dt><span class="sect1"><a href="infoschema-view-column-usage.html">37.61. <code class="literal">view_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-view-routine-usage.html">37.62. <code class="literal">view_routine_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-view-table-usage.html">37.63. <code class="literal">view_table_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-views.html">37.64. <code class="literal">views</code></a></span></dt></dl></div><a id="id-1.7.6.2" class="indexterm"></a><p> The information schema consists of a set of views that contain information about the objects defined in the current database. The information schema is defined in the SQL standard and can therefore be expected to be portable and remain stable — unlike the system catalogs, which are specific to <span class="productname">PostgreSQL</span> and are modeled after implementation concerns. The information schema views do not, however, contain information about <span class="productname">PostgreSQL</span>-specific features; to inquire about those you need to query the system catalogs or other <span class="productname">PostgreSQL</span>-specific views. </p><div class="note"><h3 class="title">Note</h3><p> When querying the database for constraint information, it is possible for a standard-compliant query that expects to return one row to return several. This is because the SQL standard requires constraint names to be unique within a schema, but <span class="productname">PostgreSQL</span> does not enforce this restriction. <span class="productname">PostgreSQL</span> automatically-generated constraint names avoid duplicates in the same schema, but users can specify such duplicate names. </p><p> This problem can appear when querying information schema views such as <code class="literal">check_constraint_routine_usage</code>, <code class="literal">check_constraints</code>, <code class="literal">domain_constraints</code>, and <code class="literal">referential_constraints</code>. Some other views have similar issues but contain the table name to help distinguish duplicate rows, e.g., <code class="literal">constraint_column_usage</code>, <code class="literal">constraint_table_usage</code>, <code class="literal">table_constraints</code>. </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ecpg-develop.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="client-interfaces.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="infoschema-schema.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">36.16. Internals </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 37.1. The Schema</td></tr></table></div></body></html>
