PostgreSQL:

CREATE INDEX

CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ name ] ON table [ USING method ]
( { column | ( expression ) } [ COLLATE collation ] [ opclass ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] )
[ WITH ( storage_parameter = value [, ... ] ) ]
[ TABLESPACE tablespace ]
[ WHERE predicate ]

Example

CREATE UNIQUE INDEX title_idx ON films (title);
CREATE INDEX ON films ((lower(title)));
CREATE INDEX title_idx_german ON films (title COLLATE "de_DE");
CREATE INDEX title_idx_nulls_low ON films (title NULLS FIRST);
CREATE UNIQUE INDEX title_idx ON films (title) WITH (fillfactor = 70);
CREATE INDEX gin_idx ON documents_table USING gin (locations) WITH
(fastupdate = off);