aspnet_membership join with tbl_country

Hi,
aspnet_membership is parent table.
tbl_country is child table.

In table aspnet_membership I must add new column ID autoinc primarykey?
Is it sufficient if I add a column in the table tbl_country new columns UserId foreignkey,
and then join aspnet_membership with UserId primarykey and table tbl_country UserId foreignkey?
 
Help.
Regards,
Dejan
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