## 37.24. `element_types`

 The view `element_types` contains the data type descriptors of the elements of arrays. When a table column, composite-type attribute, 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_type
FROM 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.collection_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 37.22. `element_types` Columns**

|                                                                                                                                                                           Column Type<br/><br/> Description                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                                                                                                             `object_catalog` `sql_identifier`<br/><br/> Name of the database that contains the object that uses the array being described (always the current database)                                                                                                              |
|                                                                                                                              `object_schema` `sql_identifier`<br/><br/> Name of the schema that contains the object that uses the array being described                                                                                                                              |
|                                                                                                                                           `object_name` `sql_identifier`<br/><br/> Name of the object that uses the array being described                                                                                                                                            |
|`object_type` `character_data`<br/><br/> The type of the object that uses the array being described: one of `TABLE` (the array is used by a column of that table), `USER-DEFINED TYPE` (the array is used by an attribute of that composite type), `DOMAIN` (the array is used by that domain), `ROUTINE` (the array is used by a parameter or the return data type of that function).|
|                                                                                `collection_type_identifier` `sql_identifier`<br/><br/> 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`<br/><br/> 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`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                  |
|                                                                                                                  `character_octet_length` `cardinal_number`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                   |
|                                                                                                                                         `character_set_catalog` `sql_identifier`<br/><br/> Applies to a feature not available in PostgreSQL                                                                                                                                          |
|                                                                                                                                          `character_set_schema` `sql_identifier`<br/><br/> Applies to a feature not available in PostgreSQL                                                                                                                                          |
|                                                                                                                                           `character_set_name` `sql_identifier`<br/><br/> Applies to a feature not available in PostgreSQL                                                                                                                                           |
|                                                                                  `collation_catalog` `sql_identifier`<br/><br/> Name of the database containing the collation of the element type (always the current database), null if default or the data type of the element is not collatable                                                                                   |
|                                                                                                   `collation_schema` `sql_identifier`<br/><br/> Name of the schema containing the collation of the element type, null if default or the data type of the element is not collatable                                                                                                   |
|                                                                                                               `collation_name` `sql_identifier`<br/><br/> Name of the collation of the element type, null if default or the data type of the element is not collatable                                                                                                               |
|                                                                                                                     `numeric_precision` `cardinal_number`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                     |
|                                                                                                                  `numeric_precision_radix` `cardinal_number`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                  |
|                                                                                                                       `numeric_scale` `cardinal_number`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                       |
|                                                                                                                    `datetime_precision` `cardinal_number`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                     |
|                                                                                                                       `interval_type` `character_data`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                        |
|                                                                                                                    `interval_precision` `cardinal_number`<br/><br/> Always null, since this information is not applied to array element data types in PostgreSQL                                                                                                                     |
|                                                                                                                                                           `domain_default` `character_data`<br/><br/> Not yet implemented                                                                                                                                                            |
|                                                                                                                     `udt_catalog` `sql_identifier`<br/><br/> Name of the database that the data type of the elements is defined in (always the current database)                                                                                                                     |
|                                                                                                                                     `udt_schema` `sql_identifier`<br/><br/> Name of the schema that the data type of the elements is defined in                                                                                                                                      |
|                                                                                                                                                     `udt_name` `sql_identifier`<br/><br/> Name of the data type of the elements                                                                                                                                                      |
|                                                                                                                                             `scope_catalog` `sql_identifier`<br/><br/> Applies to a feature not available in PostgreSQL                                                                                                                                              |
|                                                                                                                                              `scope_schema` `sql_identifier`<br/><br/> Applies to a feature not available in PostgreSQL                                                                                                                                              |
|                                                                                                                                               `scope_name` `sql_identifier`<br/><br/> Applies to a feature not available in PostgreSQL                                                                                                                                               |
|                                                                                                                        `maximum_cardinality` `cardinal_number`<br/><br/> Always null, because arrays always have unlimited maximum cardinality in PostgreSQL                                                                                                                         |
|                                                                                                                         `dtd_identifier` `sql_identifier`<br/><br/> An identifier of the data type descriptor of the element. This is currently not useful.                                                                                                                          |

