Ok thanks for the explanation. Maybe I am being dense here (not uncommon ;) but what is the difference between...
add_primary_key [:user_id, :store, :object, :fn] and index [:user_id, :store, :object, :fn], :unique => true Both seem to create a multi key unique index, what is the extra constraint that is added with primary_key? or is it different for Mysql and postgresql? Thanks On Dec 6, 2:26 pm, John W Higgins <[email protected]> wrote: > On Mon, Dec 6, 2010 at 1:37 PM, Jim Morris <[email protected]> wrote: > > Hi, > > > WRT this bug entry > >http://code.google.com/p/ruby-sequel/issues/detail?id=317 > > > I thought a primary key with multiple columns is more like an index > > not a constraint. > > Primary Keys are always a constraint. They fall within the family of Unique > Keys. > > However, most implementations will setup both the constraint and an index > because clearly one is normally interested in both. This doesn't change the > role of a primary key - it's just a nice add on that most engines help with. > > John -- You received this message because you are subscribed to the Google Groups "sequel-talk" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sequel-talk?hl=en.
