PostgreSQL : Documentation: 9.6: CREATE COLLATION : Postgres Professional

CREATE COLLATION
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CREATE COLLATION

CREATE COLLATION — define a new collation

Synopsis

CREATE COLLATION name (
    [ LOCALE = locale, ]
    [ LC_COLLATE = lc_collate, ]
    [ LC_CTYPE = lc_ctype ]
)
CREATE COLLATION name FROM existing_collation

Description

CREATE COLLATION defines a new collation using the specified operating system locale settings, or by copying an existing collation.

To be able to create a collation, you must have CREATE privilege on the destination schema.

Parameters

name: The name of the collation. The collation name can be schema-qualified. If it is not, the collation is defined in the current schema. The collation name must be unique within that schema. (The system catalogs can contain collations with the same name for other encodings, but these are ignored if the database encoding does not match.)
locale: This is a shortcut for setting LC_COLLATE and LC_CTYPE at once. If you specify this, you cannot specify either of those parameters.
lc_collate: Use the specified operating system locale for the LC_COLLATE locale category. The locale must be applicable to the current database encoding. (See CREATE DATABASE for the precise rules.)
lc_ctype: Use the specified operating system locale for the LC_CTYPE locale category. The locale must be applicable to the current database encoding. (See CREATE DATABASE for the precise rules.)
existing_collation: The name of an existing collation to copy. The new collation will have the same properties as the existing one, but it will be an independent object.

Notes

Use DROP COLLATION to remove user-defined collations.

See Section 23.2 for more information about collation support in PostgreSQL.

Examples

To create a collation from the operating system locale fr_FR.utf8 (assuming the current database encoding is UTF8):

CREATE COLLATION french (LOCALE = 'fr_FR.utf8');

To create a collation from an existing collation:

CREATE COLLATION german FROM "de_DE";

This can be convenient to be able to use operating-system-independent collation names in applications.

Compatibility

There is a CREATE COLLATION statement in the SQL standard, but it is limited to copying an existing collation. The syntax to create a new collation is a PostgreSQL extension.