CREATE TABLE paperfield (fieldid INT, paperid INT)
CREATE TABLE writes (paperid INT, authorid INT)
CREATE TABLE paperkeyphrase (paperid INT, keyphraseid INT)
CREATE TABLE journal (journalid INT, journalname VARCHAR)
CREATE TABLE dataset (datasetid INT, datasetname VARCHAR)
CREATE TABLE venue (venueid INT, venuename VARCHAR)
CREATE TABLE paperdataset (paperid INT, datasetid INT)
CREATE TABLE author (authorid INT, authorname VARCHAR)
CREATE TABLE keyphrase (keyphraseid INT, keyphrasename VARCHAR)
CREATE TABLE cite (citingpaperid INT, citedpaperid INT)
CREATE TABLE paper (paperid INT, title VARCHAR, venueid INT, year INT, numciting INT, numcitedby INT, journalid INT)
CREATE TABLE field (fieldid INT)

Who has published more papers in NSDI ?
SELECT DISTINCT COUNT(DISTINCT paper.paperid), writes.authorid FROM paper, venue, writes WHERE venue.venueid = paper.venueid AND venue.venuename = 'NSDI' AND writes.paperid = paper.paperid GROUP BY writes.authorid ORDER BY COUNT(DISTINCT paper.paperid) DESC
SELECT DISTINCT COUNT(DISTINCT "paper"."paperid"), "writes"."authorid" FROM "paper" JOIN "venue" ON "paper"."venueid" = "venue"."venueid" AND "venue"."venuename" = 'NSDI' JOIN "writes" ON "paper"."paperid" = "writes"."paperid" GROUP BY "writes"."authorid" ORDER BY COUNT(DISTINCT "paper"."paperid") DESC NULLS LAST