codekingpro/portable-devtools
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1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!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="36.17. Internals" /><link rel="next" href="infoschema-schema.html" title="37.1. The Schema" /></head><body id="docContent" class="container-fluid col-10"><div 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="36.17. 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 16.3 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 /></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-column-usage.html">37.12. <code class="literal">column_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-domain-usage.html">37.13. <code class="literal">column_domain_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-options.html">37.14. <code class="literal">column_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-privileges.html">37.15. <code class="literal">column_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-column-udt-usage.html">37.16. <code class="literal">column_udt_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-columns.html">37.17. <code class="literal">columns</code></a></span></dt><dt><span class="sect1"><a href="infoschema-constraint-column-usage.html">37.18. <code class="literal">constraint_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-constraint-table-usage.html">37.19. <code class="literal">constraint_table_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-data-type-privileges.html">37.20. <code class="literal">data_type_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-domain-constraints.html">37.21. <code class="literal">domain_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-domain-udt-usage.html">37.22. <code class="literal">domain_udt_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-domains.html">37.23. <code class="literal">domains</code></a></span></dt><dt><span class="sect1"><a href="infoschema-element-types.html">37.24. <code class="literal">element_types</code></a></span></dt><dt><span class="sect1"><a href="infoschema-enabled-roles.html">37.25. <code class="literal">enabled_roles</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-data-wrapper-options.html">37.26. <code class="literal">foreign_data_wrapper_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-data-wrappers.html">37.27. <code class="literal">foreign_data_wrappers</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-server-options.html">37.28. <code class="literal">foreign_server_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-servers.html">37.29. <code class="literal">foreign_servers</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-table-options.html">37.30. <code class="literal">foreign_table_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-foreign-tables.html">37.31. <code class="literal">foreign_tables</code></a></span></dt><dt><span class="sect1"><a href="infoschema-key-column-usage.html">37.32. <code class="literal">key_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-parameters.html">37.33. <code class="literal">parameters</code></a></span></dt><dt><span class="sect1"><a href="infoschema-referential-constraints.html">37.34. <code class="literal">referential_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-column-grants.html">37.35. <code class="literal">role_column_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-routine-grants.html">37.36. <code class="literal">role_routine_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-table-grants.html">37.37. <code class="literal">role_table_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-udt-grants.html">37.38. <code class="literal">role_udt_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-role-usage-grants.html">37.39. <code class="literal">role_usage_grants</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routine-column-usage.html">37.40. <code class="literal">routine_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routine-privileges.html">37.41. <code class="literal">routine_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routine-routine-usage.html">37.42. <code class="literal">routine_routine_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routine-sequence-usage.html">37.43. <code class="literal">routine_sequence_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routine-table-usage.html">37.44. <code class="literal">routine_table_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-routines.html">37.45. <code class="literal">routines</code></a></span></dt><dt><span class="sect1"><a href="infoschema-schemata.html">37.46. <code class="literal">schemata</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sequences.html">37.47. <code class="literal">sequences</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-features.html">37.48. <code class="literal">sql_features</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-implementation-info.html">37.49. <code class="literal">sql_implementation_info</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-parts.html">37.50. <code class="literal">sql_parts</code></a></span></dt><dt><span class="sect1"><a href="infoschema-sql-sizing.html">37.51. <code class="literal">sql_sizing</code></a></span></dt><dt><span class="sect1"><a href="infoschema-table-constraints.html">37.52. <code class="literal">table_constraints</code></a></span></dt><dt><span class="sect1"><a href="infoschema-table-privileges.html">37.53. <code class="literal">table_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-tables.html">37.54. <code class="literal">tables</code></a></span></dt><dt><span class="sect1"><a href="infoschema-transforms.html">37.55. <code class="literal">transforms</code></a></span></dt><dt><span class="sect1"><a href="infoschema-triggered-update-columns.html">37.56. <code class="literal">triggered_update_columns</code></a></span></dt><dt><span class="sect1"><a href="infoschema-triggers.html">37.57. <code class="literal">triggers</code></a></span></dt><dt><span class="sect1"><a href="infoschema-udt-privileges.html">37.58. <code class="literal">udt_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-usage-privileges.html">37.59. <code class="literal">usage_privileges</code></a></span></dt><dt><span class="sect1"><a href="infoschema-user-defined-types.html">37.60. <code class="literal">user_defined_types</code></a></span></dt><dt><span class="sect1"><a href="infoschema-user-mapping-options.html">37.61. <code class="literal">user_mapping_options</code></a></span></dt><dt><span class="sect1"><a href="infoschema-user-mappings.html">37.62. <code class="literal">user_mappings</code></a></span></dt><dt><span class="sect1"><a href="infoschema-view-column-usage.html">37.63. <code class="literal">view_column_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-view-routine-usage.html">37.64. <code class="literal">view_routine_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-view-table-usage.html">37.65. <code class="literal">view_table_usage</code></a></span></dt><dt><span class="sect1"><a href="infoschema-views.html">37.66. <code class="literal">views</code></a></span></dt></dl></div><a id="id-1.7.6.2" class="indexterm"></a><p>3 The information schema consists of a set of views that contain4 information about the objects defined in the current database. The5 information schema is defined in the SQL standard and can therefore6 be expected to be portable and remain stable — unlike the system7 catalogs, which are specific to8 <span class="productname">PostgreSQL</span> and are modeled after9 implementation concerns. The information schema views do not,10 however, contain information about11 <span class="productname">PostgreSQL</span>-specific features; to inquire12 about those you need to query the system catalogs or other13 <span class="productname">PostgreSQL</span>-specific views.14 </p><div class="note"><h3 class="title">Note</h3><p>15 When querying the database for constraint information, it is possible16 for a standard-compliant query that expects to return one row to17 return several. This is because the SQL standard requires constraint18 names to be unique within a schema, but19 <span class="productname">PostgreSQL</span> does not enforce this20 restriction. <span class="productname">PostgreSQL</span>21 automatically-generated constraint names avoid duplicates in the22 same schema, but users can specify such duplicate names.23 </p><p>24 This problem can appear when querying information schema views such25 as <code class="literal">check_constraint_routine_usage</code>,26 <code class="literal">check_constraints</code>, <code class="literal">domain_constraints</code>, and27 <code class="literal">referential_constraints</code>. Some other views have similar28 issues but contain the table name to help distinguish duplicate29 rows, e.g., <code class="literal">constraint_column_usage</code>,30 <code class="literal">constraint_table_usage</code>, <code class="literal">table_constraints</code>.31 </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" title="36.17. Internals">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="client-interfaces.html" title="Part IV. Client Interfaces">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="infoschema-schema.html" title="37.1. The Schema">Next</a></td></tr><tr><td width="40%" align="left" valign="top">36.17. Internals </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 37.1. The Schema</td></tr></table></div></body></html>