Table of Contents
information_schema_catalog_name
administrable_role_authorizations
applicable_roles
attributes
character_sets
check_constraint_routine_usage
check_constraints
collations
collation_character_set_applicability
column_column_usage
column_domain_usage
column_options
column_privileges
column_udt_usage
columns
constraint_column_usage
constraint_table_usage
data_type_privileges
domain_constraints
domain_udt_usage
domains
element_types
enabled_roles
foreign_data_wrapper_options
foreign_data_wrappers
foreign_server_options
foreign_servers
foreign_table_options
foreign_tables
key_column_usage
parameters
referential_constraints
role_column_grants
role_routine_grants
role_table_grants
role_udt_grants
role_usage_grants
routine_privileges
routines
schemata
sequences
sql_features
sql_implementation_info
sql_languages
sql_packages
sql_parts
sql_sizing
sql_sizing_profiles
table_constraints
table_privileges
tables
transforms
triggered_update_columns
triggers
udt_privileges
usage_privileges
user_defined_types
user_mapping_options
user_mappings
view_column_usage
view_routine_usage
view_table_usage
views
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 PostgreSQL and are modeled after implementation concerns. The information schema views do not, however, contain information about PostgreSQL-specific features; to inquire about those you need to query the system catalogs or other PostgreSQL-specific views.
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 PostgreSQL does not enforce this restriction. PostgreSQL automatically-generated constraint names avoid duplicates in the same schema, but users can specify such duplicate names.
This problem can appear when querying information schema views such as check_constraint_routine_usage
, check_constraints
, domain_constraints
, and referential_constraints
. Some other views have similar issues but contain the table name to help distinguish duplicate rows, e.g., constraint_column_usage
, constraint_table_usage
, table_constraints
.
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