What is the best way to implement one-one relationship ?

Secondary table must have only one record aginst each Primery Key in main table.

Dear Amr Alhawary, 

If you want a one to one (1-1) relationship then the Foreign key should itself be a Primary Key or unuiqe index in the child table that guarantees that there may be at most one row in the child table with that value.

Implementation

Create Table ParentTable

    (

    PrimaryKeyCol ... not null Primary Key

    , ...

    )

Create Table ChildTable

    (

    , ForeignKeyCol ... [not] null [Primary Key, Unique]

    , ...

    , Constraint FK_ChildTable_ParentTable

        Foreign Key ( ForeignKeyCol )

        References ParentTable( PrimaryKeyCol )

    )

I think this will help

with regards,

have same key as primary key in both tables.

where is the requirement of creating two master-child tables for one-one relationship in rdbms?, can we simply not create one table having primary key will suffice, right? and further purpose of shortening the tables, we can creates views, right? i think this may be the best solution can think of instead of having two tables.

 correct me please if i'm wrong or understood the question wrongly. thanks

 using Foreign key , you should add a column in one table that reference the other table 

yes you're totally right but i'm asking about how to do that ? the best way to do it in database

if you have a tableA with as Primary Key "PKA" and the same key exists in tableB as a primary key "PKB" a one to one relation can be established between the two tables and selecting all feilds from both using the follwing query

select a.*,b.* from tableA a,tableB b where a.PKA = a.PKB

or you can inner join like this

select a.*,b.* from tableA as a inner join tableB as b on a.PKA=b.PKB

please note that both the keys must be primary in both tables or at least the field of these keys must have a unique index (constraint)