CREATE COLLATION — define a new collation
CREATE COLLATION [ IF NOT EXISTS ]name( [ LOCALE =locale, ] [ LC_COLLATE =lc_collate, ] [ LC_CTYPE =lc_ctype, ] [ PROVIDER =provider, ] [ DETERMINISTIC =boolean, ] [ RULES =rules, ] [ VERSION =version] ) CREATE COLLATION [ IF NOT EXISTS ]nameFROMexisting_collation
   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.
  
IF NOT EXISTSDo 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.
nameThe 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.)
localeThe locale name for this collation. See Section 23.2.2.3.1 and Section 23.2.2.3.2 for details.
       If provider is libc, this
       is a shortcut for setting LC_COLLATE and
       LC_CTYPE at once.  If you specify
       locale, you cannot specify either of those
       parameters.
      
       If provider is builtin,
       then locale must be specified and set to
       either C or C.UTF-8.
      
lc_collate
       If provider is libc, use
       the specified operating system locale for the
       LC_COLLATE locale category.
      
lc_ctype
       If provider is libc, 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 builtin,
       icu (if
       the server was built with ICU support) or libc.
       libc is the default.  See Section 23.1.4 for details.
      
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 LOCALE setting
       and set the collation to not deterministic here.
      
Nondeterministic collations are only supported with the ICU provider.
rulesSpecifies additional collation rules to customize the behavior of the collation. This is supported for ICU only. See Section 23.2.3.4 for details.
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 for how to handle collation version mismatches.
existing_collationThe 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.
   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 23.2.2.3 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 for the precise rules.
  
   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 using the ICU provider, based on the root ICU locale, with custom rules:
CREATE COLLATION custom (provider = icu, locale = 'und', rules = '&V << w <<< W');
See Section 23.2.3.4 for further details and examples on the rules syntax.
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.
   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.