Hi,
I have seen few examples in docs that creates tables having primary key column , but explicitly defined again with NOT NULL constraint. I don't understand why is this needed...
create table cars( c_id number not null,
c_name varchar2(30),
Constraint Pk_c_id Primary Key (c_id));
A primary key itself is combination of not null + unique. but some of docs examples again use explicit NOT NULL declaration fro a primary key column which becomes DOUBLE NOT NULL . Please help me on this .Thnks.