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CREATE COLLATION(7)	  PostgreSQL 18.6 Documentation      CREATE COLLATION(7)

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, ]
	 [ RULES = rules, ]
	 [ VERSION = version ]
     )
     CREATE COLLATION [ IF NOT EXISTS ] name FROM existing_collation

DESCRIPTION
     CREATE COLLATION defines a new collation using the specified operating sys-
     tem 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 col-
	 lation 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
	 The  locale  name  for  this collation. See Section 23.2.2.3.1 and Sec-
	 tion 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, C.UTF-8 or PG_UNICODE_FAST.

     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 logi-
	 cally 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.

     rules
	 Specifies additional collation rules to customize the behavior  of  the
	 collation. This is supported for ICU only. See Section 23.2.3.4 for de-
	 tails.

     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 colla-
	 tion 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-conflict-
     ing,  on the pg_collation system catalog, so only one CREATE COLLATION com-
     mand 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 (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 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  col-
     lation names in applications.

COMPATIBILITY
     There  is	a CREATE COLLATION statement in the SQL standard, but it is lim-
     ited 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))

PostgreSQL 18.6 		      2026		     CREATE COLLATION(7)

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