How can I make sure there are no duplicate records when using Data Import Wizard?

Environment:

Data Import Wizard

Resolution:

The Data Import Wizard has a 'Duplicate Criteria' section.

The Duplicate Criteria section of the Data Import Wizard displays the criteria used to prevent instances of redundant records. During the upload process, fields listed in the criteria are compared with existing values in the contacts table in search of duplicate records. When a duplicate is found, action will be taken as specified in the Duplicate Records drop-down menu on the wizard's initial page.

For added flexibility, you can define custom criteria by clearing the Use Default check box and entering a logical expression using any combination of mapped fields. For instance, if you want to avoid creating duplicate records with the same last name (mapped to column 1) and user ID (mapped to column 2), you can enter last_name={1} AND login={2}. If column headers have been specified in the data file or header file, you can refer to them by header name instead, such as last_name={Last Name} AND login={User ID}.

Note: It is important to ensure one of two things is true before executing the upload:

1. The 'Use Default' box should be checked.
   This will  add the expression 'any_email={Contact Email} to the 'Criteria' section to ensure the records to be uploaded do not match an existing email, email_alt1, and email_alt2) field in the contacts table.
2. If the 'Use Default' box is unchecked, be sure the 'Criteria' box is not left empty, else there is no expression used in checking for duplicate contacts and will result in the contact being inserted into the database with '.0001' appended to the contact's email address.  Note:  Each field in the duplicate criteria must be an Indexed field".