>I have a DWH query which IMHO should do partition prunning but it does not. >The query is as follows... With your query, the CBO can't be sure that only one value of FE_DIA will be returned (BTW, perhaps it could tell that if FE_DIA's the one and only PK column for PRM_FEDIA), Try replacing the join to PRM_FEDIA with a scalar subquery - then the optimiser should be able to tell that only one value for FE_DIA can be referenced. SELECT a11.id_tp_busq id_tp_busq, a14.dt_busqueda dt_busqueda, a11.id_site id_site, a13.de_site de_site, SUM (a11.nt_busqueda) wjxbfs1 FROM prm_site a13, prm_tibusqbrs a14, prh_bqbusq a11 -- PARTITIONED BY FE_DIA WHERE a11.fe_dia = (SELECT fe_dia FROM prm_fedia WHERE id_mes = 200611) AND a11.id_site = a13.id_site AND a11.id_tp_busq = a14.id_tp_busq AND a13.id_site = 1 AND a11.tx_termino LIKE 'Without usage%' GROUP BY a11.id_tp_busq, a14.dt_busqueda, a11.id_site, a13.de_site Regards Nigel