character_sets
The view character_sets identifies the character
sets available in the current database. Since PostgreSQL does not
support multiple character sets within one database, this view only
shows one, which is the database encoding.
Take note of how the following terms are used in the SQL standard:
An abstract collection of characters, for
example UNICODE, UCS, or
LATIN1. Not exposed as an SQL object, but
visible in this view.
An encoding of some character repertoire. Most older character
repertoires only use one encoding form, and so there are no
separate names for them (e.g., LATIN1 is an
encoding form applicable to the LATIN1
repertoire). But for example Unicode has the encoding forms
UTF8, UTF16, etc. (not
all supported by PostgreSQL). Encoding forms are not exposed
as an SQL object, but are visible in this view.
A named SQL object that identifies a character repertoire, a
character encoding, and a default collation. A predefined
character set would typically have the same name as an encoding
form, but users could define other names. For example, the
character set UTF8 would typically identify
the character repertoire UCS, encoding
form UTF8, and some default collation.
You can think of an “encoding” in PostgreSQL either as a character set or a character encoding form. They will have the same name, and there can only be one in one database.
Table 37.5. character_sets Columns
| Name | Data Type | Description |
|---|---|---|
character_set_catalog | sql_identifier | Character sets are currently not implemented as schema objects, so this column is null. |
character_set_schema | sql_identifier | Character sets are currently not implemented as schema objects, so this column is null. |
character_set_name | sql_identifier | Name of the character set, currently implemented as showing the name of the database encoding |
character_repertoire | sql_identifier | Character repertoire, showing UCS if the encoding is UTF8, else just the encoding name |
form_of_use | sql_identifier | Character encoding form, same as the database encoding |
default_collate_catalog | sql_identifier | Name of the database containing the default collation (always the current database, if any collation is identified) |
default_collate_schema | sql_identifier | Name of the schema containing the default collation |
default_collate_name | sql_identifier |
Name of the default collation. The default collation is
identified as the collation that matches
the COLLATE and CTYPE
settings of the current database. If there is no such
collation, then this column and the associated schema and
catalog columns are null.
|