why this query takes so much time to execute ?please suggest for about efficiency of this query and is there is any better way to write this? : select Date,NeName,KPINAME,SUB_TYPE1,KPI from ggsn_kpi_2017 where date in ('2017-08-19','2017-08-18','2017-08-17','2017-08-16','2017-08-15','2017-08-14','2017-08-13') and KPINAME in('SM_SUCC_SESS_ACT_GGSN','SM_FAIL_SESS_ACT_GGSN','SM_SUCC_SESS_ACT_P_GW','SM_FAIL_SESS_ACT_P_GW','SM_SUCC_SESS_ACT_SAE_GW','SM_FAIL_SESS_ACT_SAE_GW','SM_DOWNLINK_BYTES_M2M','SM_UPLINK_BYTES_M2M') group by Date,NeName,KPINAME union select Date,NeName,KPINAME,SUB_TYPE1,KPI from ggsn_kpi_2016 where date in ('2017-08-19','2017-08-18','2017-08-17','2017-08-16','2017-08-15','2017-08-14','2017-08-13') and KPINAME in('SM_SUCC_SESS_ACT_GGSN','SM_FAIL_SESS_ACT_GGSN','SM_SUCC_SESS_ACT_P_GW','SM_FAIL_SESS_ACT_P_GW','SM_SUCC_SESS_ACT_SAE_GW','SM_FAIL_SESS_ACT_SAE_GW','SM_DOWNLINK_BYTES_M2M','SM_UPLINK_BYTES_M2M') group by Date,NeName,KPINAME