Hi, more detais needed.Do all with same connection 1. Connect to db2. Run query without where clause SELECT
A.cd_xxx, A.dt_1, A.dt_2, A.dt_3, A.dt_4, A.dt_5, A.dt_index FROM DM251 A 3. Run query SELECT A.cd_xxx, A.dt_1, A.dt_2, A.dt_3, A.dt_4, A.dt_5, A.dt_index FROM DM251 A WHERE A.DT_INDEX IS NULL 4. Run querySELECT A.cd_xxx, A.dt_1, A.dt_2, A.dt_3, A.dt_4, A.dt_5, A.dt_index FROM DM251 A WHERE A.DT_INDEX IS Not NULL 5. Disconnect from db What are time stats of point 2,3,4? Regards,Karol Bieniaszewski -------- Oryginalna wiadomość --------Od: "Hugo Eyng hugoe...@msn.com [firebird-support]" <firebird-support@yahoogroups.com> Data: 09.10.2018 16:46 (GMT+01:00) Do: firebird-support@yahoogroups.com Temat: [firebird-support] Very slow select Index with null date Hello. I created an index on a table where de column is datetime type. The problem seems to be related to the NULL value. This SQL is very SLOW (about 7 seconds for a table containing 360.000 records). Returns around 400 records SELECT A.cd_xxx, A.dt_1, A.dt_2, A.dt_3, A.dt_4, A.dt_5, A.dt_index FROM DM251 A WHERE A.DT_INDEX IS NULL This SQL is very FAST (less than 0.5 seconds for a table containing 360.000 records). Returns around 359.600 records SELECT A.cd_xxx, A.dt_1, A.dt_2, A.dt_3, A.dt_4, A.dt_5, A.dt_index FROM DM251 A WHERE A.DT_INDEX IS NOT NULL Atenciosamente, + + Hugo Eyng + +