CREATE TABLE author (aid INT, homepage VARCHAR, name VARCHAR, oid INT)
CREATE TABLE journal (homepage VARCHAR, jid INT, name VARCHAR)
CREATE TABLE domain_journal (did INT, jid INT)
CREATE TABLE publication (abstract VARCHAR, cid INT, citation_num INT, jid INT, pid INT, reference_num INT, title VARCHAR, year INT)
CREATE TABLE keyword (keyword VARCHAR, kid INT)
CREATE TABLE domain_conference (cid INT, did INT)
CREATE TABLE conference (cid INT, homepage VARCHAR, name VARCHAR)
CREATE TABLE writes (aid INT, pid INT)
CREATE TABLE domain_keyword (did INT, kid INT)
CREATE TABLE domain_publication (did INT, pid INT)
CREATE TABLE organization (continent VARCHAR, homepage VARCHAR, name VARCHAR, oid INT)
CREATE TABLE publication_keyword (kid INT, pid INT)
CREATE TABLE cite (cited INT, citing INT)
CREATE TABLE domain_author (aid INT, did INT)
CREATE TABLE domain (did INT, name VARCHAR)

return me the number of keywords in PVLDB .
SELECT COUNT(DISTINCT (keyword.keyword)) FROM journal, keyword, publication, publication_keyword WHERE journal.name = 'PVLDB' AND publication_keyword.kid = keyword.kid AND publication.jid = journal.jid AND publication.pid = publication_keyword.pid
SELECT COUNT(DISTINCT "keyword"."keyword") FROM "journal" JOIN "publication" ON "journal"."jid" = "publication"."jid" JOIN "publication_keyword" ON "publication"."pid" = "publication_keyword"."pid" JOIN "keyword" ON "keyword"."kid" = "publication_keyword"."kid" WHERE "journal"."name" = 'PVLDB'