if you want to create relations between two tables, on of logins and other of details, you can do something like..
table user
user_id
user_username
user_password
table user_details
id
user_id
name
contact
(..)
and you relate the field "user_id" in the 'user' table to the field 'user_id' in the 'user_details' table.
wich goes..
user
id | username | password
1 | hisname | hispass
2 | name | passwrd
user_details
id | user_id | name | contact
1 | 1 | jan | '4041230423
2 | 2 | eqwe | 4214321412412
where user 'hisname' is called 'jan'
and
user 'name' is called 'eqwe'
