PostgreSQL 8.0.1 Documentation
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30.16. `element_types`

The view element_types contains the data type descriptors of the elements of arrays. When a table column, domain, function parameter, or function return value is defined to be of an array type, the respective information schema view only contains ARRAY in the column data_type. To obtain information on the element type of the array, you can join the respective view with this view. For example, to show the columns of a table with data types and array element types, if applicable, you could do

SELECT c.column_name, c.data_type, e.data_type AS element_typeFROM information_schema.columns c LEFT JOIN information_schema.element_types e ON ((c.table_catalog, c.table_schema, c.table_name, 'TABLE', c.dtd_identifier) = (e.object_catalog, e.object_schema, e.object_name, e.object_type, e.array_type_identifier))WHERE c.table_schema = '...' AND c.table_name = '...'ORDER BY c.ordinal_position;

This view only includes objects that the current user has access to, by way of being the owner or having some privilege.

Table 30-14. element_types Columns

Name	Data Type	Description
`object_catalog`	`sql_identifier`	Name of the database that contains the object that uses the array being described (always the current database)
`object_schema`	`sql_identifier`	Name of the schema that contains the object that uses the array being described
`object_name`	`sql_identifier`	Name of the object that uses the array being described
`object_type`	`character_data`	The type of the object that uses the array being described: one of `TABLE` (the array is used by a column of that table), `DOMAIN` (the array is used by that domain), `ROUTINE` (the array is used by a parameter or the return data type of that function).
`array_type_identifier`	`sql_identifier`	The identifier of the data type descriptor of the array being described. Use this to join with the `dtd_identifier` columns of other information schema views.
`data_type`	`character_data`	Data type of the array elements, if it is a built-in type, else `USER-DEFINED` (in that case, the type is identified in `udt_name` and associated columns).
`character_maximum_length`	`cardinal_number`	Always null, since this information is not applied to array element data types in PostgreSQL
`character_octet_length`	`cardinal_number`	Always null, since this information is not applied to array element data types in PostgreSQL
`character_set_catalog`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`character_set_schema`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`character_set_name`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`collation_catalog`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`collation_schema`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`collation_name`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`numeric_precision`	`cardinal_number`	Always null, since this information is not applied to array element data types in PostgreSQL
`numeric_precision_radix`	`cardinal_number`	Always null, since this information is not applied to array element data types in PostgreSQL
`numeric_scale`	`cardinal_number`	Always null, since this information is not applied to array element data types in PostgreSQL
`datetime_precision`	`cardinal_number`	Always null, since this information is not applied to array element data types in PostgreSQL
`interval_type`	`character_data`	Always null, since this information is not applied to array element data types in PostgreSQL
`interval_precision`	`character_data`	Always null, since this information is not applied to array element data types in PostgreSQL
`domain_default`	`character_data`	Not yet implemented
`udt_catalog`	`sql_identifier`	Name of the database that the data type of the elements is defined in (always the current database)
`udt_schema`	`sql_identifier`	Name of the schema that the data type of the elements is defined in
`udt_name`	`sql_identifier`	Name of the data type of the elements
`scope_catalog`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`scope_schema`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`scope_name`	`sql_identifier`	Applies to a feature not available in PostgreSQL
`maximum_cardinality`	`cardinal_number`	Always null, because arrays always have unlimited maximum cardinality in PostgreSQL
`dtd_identifier`	`sql_identifier`	An identifier of the data type descriptor of the element. This is currently not useful.

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30.16. element_types

30.16. `element_types`