Which is better Index

Dear all,

 I want to clear my doubts regarding creating several single or a multi-column indexes.
My table schema is :-
CREATE TABLE svo2(  svo_id bigint NOT NULL DEFAULT nextval('svo_svo_id_seq'::regclass),  doc_id integer,  sentence_id integer,  clause_id integer,  negation integer,  subject charactervarying(3000),  verb character varying(3000),  "object" character varying(3000),  preposition character varying(3000),  subject_type character varying(3000),  object_type charactervarying(3000),  subject_attribute character varying(3000),  object_attribute character varying(3000),  verb_attribute character varying(3000),  subject_concept character varying(100), object_concept character varying(100),  subject_sense character varying(100),  object_sense character varying(100),  subject_chain character varying(5000),  object_chain character varying(5000),  sub_type_id integer,  obj_type_id integer,  CONSTRAINT pk_svo_id PRIMARY KEY (svo_id))WITH (  OIDS=FALSE);


Fore.g

CREATE INDEX idx_svo2_id_dummy  ON svo2  USING btree (doc_id, clause_id, sentence_id);

or

CREATE INDEX idx_svo2_id_dummy  ON svo2  USING btree (doc_id);
CREATE INDEX idx_svo2_id_dummy1  ON svo2  USING btree (clause_id);
CREATE INDEX idx_svo2_id_dummy2  ON svo2  USING btree (sentence_id);

Which is better if a query uses all three columns in join where clause.



Thanks & best regards,
Adarsh Sharma