How can i add records after the existing records in the existing excel file using php?
The simplest process is a clone copy of the target table, with a relationship to the real table based on whatever field or set of fields constitutes a verifiably unique identity (i.e., makes it a duplicate or not). Import all recs into the clone table, then loop through the found set; if there is no corresponding record in the live/real table, mark it, otherwise don't mark it, go to next, exit after last, end loop. Then find the non-marked records, delete them all. Then either write out the marked ones (with a series of Set Field script steps) to the live/real table or export them as a batch to an Excel file or a Merge file and then turn around and import them into the live/real table. Finally delete all recs from the clone table since it's just a holding tank.