question about oracle and specifying primary keys....

[laFiera]

CREATE TABLE customer
(custid NUMBER(5) CONSTRAINT customer_custid_pk PRIMARY KEY,
last VARCHAR2(30) CONSTRAINT customer_last_nn NOT NULL,
first VARCHAR2(30));

what's the difference in specifying the primary key as above or just saying????

CREATE TABLE customer
(custid NUMBER(5) not null unique,
last VARCHAR2(30) CONSTRAINT customer_last_nn NOT NULL,
first VARCHAR2(30),
primary (custid);

 

[manly]

The only real difference is that in the first case, you named the primary key constraint, which Oracle recommends.

A primary key constraint implies not null and unique, so in the second case, those constraints are redundant.

I'm not an SQL expert, but I think giving a simple constraint such as not null a formal name is unnecessary.