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)

papers before 2010 about character recognition
SELECT DISTINCT paper.paperid FROM keyphrase, paper, paperkeyphrase WHERE keyphrase.keyphrasename = 'character recognition' AND paperkeyphrase.keyphraseid = keyphrase.keyphraseid AND paper.paperid = paperkeyphrase.paperid AND paper.year < 2010
SELECT DISTINCT "paper"."paperid" FROM "keyphrase" JOIN "paperkeyphrase" ON "keyphrase"."keyphraseid" = "paperkeyphrase"."keyphraseid" JOIN "paper" ON "paper"."paperid" = "paperkeyphrase"."paperid" AND "paper"."year" < 2010 WHERE "keyphrase"."keyphrasename" = 'character recognition'