Importing and linking contacts with managers

Hi All,

We have to import more than 10000 contacts of multiple accounts with mangers.

There must be duplication issues when linking manager names to contacts.

My Solution:

We have employee ID column  for all contacts as well. We may use Employee ID values in two columns.  map one column with Contact external ID field in CRM and another with actual Employee ID field in CRM.

After complete import of contacts first time, update all contacts now with manager Employee ID, and map this column with Manager External ID.

  Import file csv (first time when creating record)

Employee ID

First name