>When I need to just enter country only I'll use dcountry1.dbf. dstate1.dbf when I'll need only to enter state in respect of country.
>
>Actually, I am preparing an address book where user could store data as per his choice. If the user does not need district will not use ddistrict1.dbf. Others who need district will make entry in the ddistrict1.dbf
>
>All the three .dbfs to be used in separate combo of related fields in the address entry form.
>
>regards.

Well still they're redundant IMHO. A list of countries only could be derived from 3rd, and a list of states of a particular (or all) country could be derived from there as well. ie:

* Combo listing countries only
with thisform.myCountryCombo
.RowSourceType = 3
.RowSource = "select distinct country from table3rd order by 1"+;
  " into cursor crsCountries"
endwith

* Combo listing states of combo1's selected country only
with thisform.myCountryCombo
.RowSourceType = 3
.RowSource = "select state from table3rd order by 1"+;
  " where Country == crsCountries.Country"+;
  " into cursor crsStates"
endwith


* Combo listing districts of combo2's selected country&state
with thisform.myCountryCombo
.RowSourceType = 3
.RowSource = "select district,state,country from table3rd order by 1"+;
  " where Country == crsStates.Country"+;
  " and State == crsStates.State"+;
  " into cursor crsDistricts" && select * but show district only
 .ColumnCount=1
endwith

If you'd still go with 3 tables then besides your candidate keys (use candidate only for your unicity check) add an autogenerated surrogate primary key to each table. ie:
table1: PK:countryID
table2: PK:stateID FK:countryID
table3: PK:districtID FK:stateID
Cetin