Question

If a field does not allow to enter duplicate values and its value cannot be left blank, then it is known as ​

Answer 1

Answer:

Set the field's Indexed property to Yes (No duplicates)    You can do this by opening the table in Design view. This method is easy and a good choice if you only want to change one field at a time.

Create a data-definition query that creates the unique index    You can do this by using SQL view. This method is not as easy as using Design view, but has an advantage: you can save the data-definition query and use it again later. This is useful if you periodically delete and re-create tables and want to use unique indexes on some of the fields.