Tony / Phil, my 2c on the Primary Key definition / usage. If you have any SQL / DDL code that disagrees with the definitions below could you please repost them.
"Tony Reina" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > [EMAIL PROTECTED] (Phill Kenoyer) wrote in message news:<[EMAIL PROTECTED]>... > > Here is a good one. I have three fields set for my primary key. Now I > > thought that a primary key was unique, and dups can not be inserted. > > > > I don't think primary keys per se are unique, but rather can be made > unique by specifying that option. IIRC primary keys just allow you to > index searches within the database. So to make a unique primary key > from your db schema: > The definition of a primary key was that it WAS a unique identifier for the table Definition: The primary key of a relational table uniquely identifies each record in the table. It can either be a normal attribute that is guaranteed to be unique (such as Social Security Number in a table with no more than one record per person) or it can be generated by the DBMS (such as a globally unique identifier, or GUID, in Microsoft SQL Server). Ref: http://databases.about.com/library/glossary/bldef-primarykey.htm Also PRIMARY KEY This column is a primary key, which implies that uniqueness is enforced by the system and that other tables may rely on this column as a unique identifier for rows. See PRIMARY KEY for more information. AND The PRIMARY KEY column constraint specifies that a column of a table may contain only unique (non-duplicate), non-NULL values. The definition of the specified column does not have to include an explicit NOT NULL constraint to be included in a PRIMARY KEY constraint. Ref: http://www.ninthwonder.com/info/postgres/user/sql-createtable.htm Regards sb > > CREATE TABLE "inventory" ( > "stock" character varying(50) NOT NULL, > "inventory_type" character varying(20) DEFAULT 'unknown' NOT > NULL, > "client_id" integer NOT NULL, > [...] > UNIQUE ("stock", "inventory_type", "client_id") > Constraint "inventory_pkey" > Primary Key ("stock", "inventory_type", "client_id") > ); > > HTH, > -Tony > > > BTW, I'm using Google newsgroups to view the Postgres messages, but > haven't seen posted messages in several days on the Hackers list. Does > anyone know if this is a Google glitch or is the hackers list just not > very active during the holiday? ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
