While working on Import Set, there is a source table and target table , when I import using import s

[Abhishek Kathe]

While working on Import Set, there is a source table and target table , when I import using import set then there are duplicate records get created in my 'contact name' field's reference table . I want to restrict it without data loss
field - contact name 

type - reference

[Weird]

For references and choices there's an option in the field map called "Choice action" with options create, ignore and reject. If you don't want to create new choices, then select ignore. Create will create a new choice or option.
However choice should only create new ones if it doesn't find a match, so if you don't want to ignore it completely you have to make sure you've set the "Referenced value field name" to match your value.
For example if you're matching a location name to a location in location table, you'd set that field to name, so that the transform map knows to compare your row value to the name of an existing location.
Selecting reject will skip the whole row, so don't use that unless you want to completely ignore a row if it has certain choice in it.

[Abhishek Kathe]

Already the records present in reference field is same as in contact name still it is creating a duplicate records in reference field

[Weird]

Are you sure? Is the referenced value field name set? Is your source value identical? For example sometimes issues might come from extra spaces like "hello" vs " hello". I'm not sure, but possibly "hello" and "Hello" would also be different.

[Abhishek Kathe]

values are in numbers