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

When does Michael Stonebraker publish the GIS Database paper ?
SELECT DISTINCT paper.year FROM author, keyphrase, paper, paperkeyphrase, writes WHERE author.authorname = 'Michael Stonebraker' AND keyphrase.keyphrasename = 'GIS Database' AND paperkeyphrase.keyphraseid = keyphrase.keyphraseid AND paper.paperid = paperkeyphrase.paperid AND writes.authorid = author.authorid AND writes.paperid = paper.paperid
SELECT DISTINCT "paper"."year" FROM "author" JOIN "writes" ON "author"."authorid" = "writes"."authorid" JOIN "paper" ON "paper"."paperid" = "writes"."paperid" JOIN "paperkeyphrase" ON "paper"."paperid" = "paperkeyphrase"."paperid" JOIN "keyphrase" ON "keyphrase"."keyphraseid" = "paperkeyphrase"."keyphraseid" AND "keyphrase"."keyphrasename" = 'GIS Database' WHERE "author"."authorname" = 'Michael Stonebraker'