[GENERAL] SQL query not returning the value expected !!!!!!!!!!!!!!!!!!

[Najib Abi Fadel]

Hi if you take  a look at the following query's you can see that the third query should logically return  043219 but instead it's not returning any rows ?? What's happening ??????????????   dragon=> SELECT cod_etu from parcours_v where cod_etu = '043219';  cod_etu --------- (0 rows)   dragon=> SELECT cod_etu from parcours_hors_cursus_v where cod_etu = '043219';  cod_etu ---------  043219 (1 row)   dragon=> SELECT cod_etu from parcours_hors_cursus_v where cod_etu ='043219' and cod_etu not in (select cod_etu from parcours_v);  cod_etu --------- (0 rows)