NAME

       CREATE_COLLATION - define a new collation

SYNOPSIS

       CREATE COLLATION [ IF NOT EXISTS ] name (
           [ LOCALE = locale, ]
           [ LC_COLLATE = lc_collate, ]
           [ LC_CTYPE = lc_ctype, ]
           [ PROVIDER = provider, ]
           [ DETERMINISTIC = boolean, ]
           [ VERSION = version ]
       )
       CREATE COLLATION [ IF NOT EXISTS ] 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

       IF NOT EXISTS
           Do not throw an error if a collation with the same name already exists. A notice is
           issued in this case. Note that there is no guarantee that the existing collation is
           anything like the one that would have been created.

       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.

       lc_ctype
           Use the specified operating system locale for the LC_CTYPE locale category.

       provider
           Specifies the provider to use for locale services associated with this collation.
           Possible values are: icu, libc.  libc is the default. The available choices depend on
           the operating system and build options.

       DETERMINISTIC
           Specifies whether the collation should use deterministic comparisons. The default is
           true. A deterministic comparison considers strings that are not byte-wise equal to be
           unequal even if they are considered logically equal by the comparison. PostgreSQL
           breaks ties using a byte-wise comparison. Comparison that is not deterministic can
           make the collation be, say, case- or accent-insensitive. For that, you need to choose
           an appropriate LC_COLLATE setting and set the collation to not deterministic here.

           Nondeterministic collations are only supported with the ICU provider.

       version
           Specifies the version string to store with the collation. Normally, this should be
           omitted, which will cause the version to be computed from the actual version of the
           collation as provided by the operating system. This option is intended to be used by
           pg_upgrade for copying the version from an existing installation.

           See also ALTER COLLATION (ALTER_COLLATION(7)) for how to handle collation version
           mismatches.

       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

       CREATE COLLATION takes a SHARE ROW EXCLUSIVE lock, which is self-conflicting, on the
       pg_collation system catalog, so only one CREATE COLLATION command can run at a time.

       Use DROP COLLATION to remove user-defined collations.

       See Section 24.2.2.3 for more information on how to create collations.

       When using the libc collation provider, the locale must be applicable to the current
       database encoding. See CREATE DATABASE (CREATE_DATABASE(7)) for the precise rules.

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 using the ICU provider using German phone book sort order:

           CREATE COLLATION german_phonebook (provider = icu, locale = 'de-u-co-phonebk');

       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.

SEE ALSO

       ALTER COLLATION (ALTER_COLLATION(7)), DROP COLLATION (DROP_COLLATION(7))