return me the number of papers published in the VLDB conference before 2000 .
SELECT COUNT ( DISTINCT t2.title ) FROM publication AS t2 JOIN conference AS t1 ON t2.cid  =  t1.cid WHERE t1.name  =  "VLDB" AND t2.year  <  2000;
SELECT COUNT ( DISTINCT t2.title ) FROM publication AS t2 JOIN conference AS t1 ON t2.cid  =  t1.cid WHERE t1.name  =  "VLDB" AND t2.year  <  2000;
[{'COUNT ( DISTINCT t2.title )': 0}]