Thanks for your advise Sohaib.
The records that I removed from above tables are not historical data or from existing employees in the company. The situation of my issue is that while entering data if a new worker in Employment details, first I got error message regarding employment start date. After closing the Worker form accidentally, I intend to back to that worker to edit Employment start date, but I couldn't. It didn't show the worker that I've just entered even though I tried to filter by Name, Search name & Personnel number (I didn't filter by using other fields like Telephone, Extension because I didn't enter data into these fields). Guessing that the worker that I entered before was not recorded in table, I tried to re-enter that worker & since then, I got error message "This personnel number is already in use. Enter a new personnel number" ...
At present, my issue was solved after I found & removed unwanted records from HcmWorker, HcmEmployment, HcmPersonPrivateDetails, DirPerson, DirPartyTable, LogisticsElectronicAddress based on their relationships. In fact, using PersonnelNumber, Partition & other fields (ModifiedBy, ModifiedDateTime, CreatedBy, CreatedDateTime to make sure I worked on my records on a specific date time), I could locate a worker record that I entered & existed in table HcmWorker (for some reason, this record was not shown in Worker form in AX). Then based on their relationship between HcmWorker and other table including HcmEmployment, HcmPersonPrivateDetails, DirPerson, DirPartyTable & LogisticsElectronicAddress via the following fields such Person, RecID, Partion, PriavteOrPartyWorker, NameAlias, etc. I could find out more children records that related to the record-not-shown in HcmWorker.
Now my worker database is neat & clean & I already added the new worker that I need into AX successfully. Nothing wrong with my existing worker data at all.
Thanks
Thai