Hello, With this query : SELECT count(*) FROM tmp__pierre2 SRC INNER JOIN ref__at_lm_chapitres SUB ON SRC.siteniveau1=SUB.site AND SRC.chapitreniveau1=SUB.idchapitre1; SELECT count(*) FROM tmp__pierre2; +------------+ | L1 | +============+ | 1 061 964 254 | SELECT count(*) FROM ref__at_lm_chapitres; +---------+ | L1 | +=========+ | 1 331 867 | after several hours of running the query is still not finished and I stopped how to find out where the problem? thanks Pierre -- 1G6 52 route de bischwiller 67300 Schiltigheim Société de Services et de Formations en Logiciels Libres http://1g6.biz Tél : 06 64 63 70 35