Hello, Some times the primary key is the same as the foreign key such as in the following design. which is used to model 1-1 relationship. In the database books, such as database fundamentals(Masri), the 1-1 relation is modeled by having two separate key. when this kind of design (shared key) is preferable and is there any anomalies to it.
create table Table1 ( T1_Id integer not null primary key , T1_Data varchar(9) not null ) create table Table2 ( T2_Id integer not null primary key , T2_Data varchar(37) not null , foreign key (T2_Id) references Table1 (T1_Id) ) Thanks in advance