You could invert your solution. Create a temporary table which contains all of the existing keys, and every time you insert a new item, delete that item's key from the temporary table. At the end, do something like 'DELETE FROM main_table WHERE key IN (SELECT key FROM tmp_table)'.
-scott On 9/6/07, Andre du Plessis <[EMAIL PROTECTED]> wrote: > Im importing data > > The data has a unique value, call it MD5 for now that could be a unique > value for the data. > > > > Each record that gets imported is converted to MD5, a lookup is done on > the table for that MD5, > > if found it must leave it alone, if not found it must insert a new > record... > > > > All the items in the table that was not imported must be deleted... > > > > The only feasible approach I have is to add a column to the table, like > UPDATE_FLAG for example, > > During the import update_flag gets set to 0, > > Once a record is found update_flag gets set to 1, > > > > At the end of the import all records with update_flag = 0 gets > deleted... > > > > However I did not want to add a column to the table, REASON being, I'm > also version controlling the DB, and when an import occurs and nothing > > Has been added or removed, I don't want modifications to the DB, as the > import can run many times over. > > > > I was considering the following: > > Create a temp table call it, > > Temp_ids for example > > Then insert into the temp table for each record that was found... > > > > At the end do something like > > Delete from imports where import_id not in (select id from temp_ids) > > > > But that might be horribly slow and memory expensive remembering that > the import table may have millions of records.. > > > > What could the people here suggest to me, > > > > Thanks. > > ----------------------------------------------------------------------------- To unsubscribe, send email to [EMAIL PROTECTED] -----------------------------------------------------------------------------
