is primary key necessary

[Hari patnaik]

Hi All

I am reading Hibernate docs. I was trying a simple example which is simple select.
My question for you is do we need to have a primary key on every table which is being accessed from Hibernate

Regards
Hari

[Paul Sturrock]

You need a primary key on every entity in a relational database, regardless of whether you use Hibernate or any other tool to access the data. "Relational" data without a unique identifier is not relational.
[ December 06, 2005: Message edited by: Paul Sturrock ]

[Scott Selikoff]

That's not completely true, for tables with small enough number of columns, the primary key can be implied as the row itself. For example, if you have a set of students and a set of classes you may have a table IN_CLASS that just contains a student_id and a class_id. The record itself would be its own primary key.

[Paul Sturrock]

In which case it should be defined as a composite key (a composite key is more properly refered to as a "composite primary key"). I'm not suggesting every entity should have a surrogate key (though there are technical reasons which suggest that this might a good idea). But every table in a relational database must have a primary key, otherwise what is stored in the table is not relational data.
[ December 06, 2005: Message edited by: Paul Sturrock ]