Relational Types on Openerp

one2one:	A one2one field expresses a one:to:one relation between two objects. It is deprecated. Use many2one instead. Syntax: fields.one2one('other.object.name', 'Field Name')
many2one:	Associates this object to a parent object via this Field. For example Department an Employee belongs to would Many to one. i.e Many employees will belong to a Department Syntax: fields.many2one( 'other.object.name', 'Field Name', optional parameters) Optional parameters: ondelete: What should happen when the resource this field points to is deleted. Predefined value: “cascade”, “set null”, “restrict”, “no action”, “set default” Default value: “set null” required: True readonly: True select: True - (creates an index on the Foreign Key field) Example 'commercial': fields.many2one( 'res.users', 'Commercial', ondelete='cascade'),
one2many:	TODO Syntax: fields.one2many( 'other.object.name', 'Field relation id', 'Fieldname', optional parameter) Optional parameters: invisible: True/False states: ? readonly: True/False Example 'address': fields.one2many( 'res.partner.address', 'partner_id', 'Contacts'),
many2many:	TODO Syntax: fields.many2many('other.object.name', 'relation object', 'actual.object.id', 'other.object.id', 'Field Name') Where: other.object.name is the other object which belongs to the relation relation object is the table that makes the link actual.object.id and other.object.id are the fields’ names used in the relation table Example: 'category_ids': fields.many2many( 'res.partner.category', 'res_partner_category_rel', 'partner_id', 'category_id', 'Categories'), To make it bidirectional (= create a field in the other object): class other_object_name2(osv.osv): _inherit = 'other.object.name' _columns = { 'other_fields': fields.many2many( 'actual.object.name', 'relation object', 'actual.object.id', 'other.object.id', 'Other Field Name'), } other_object_name2() Example: class res_partner_category2(osv.osv): _inherit = 'res.partner.category' _columns = { 'partner_ids': fields.many2many( 'res.partner', 'res_partner_category_rel', 'category_id', 'partner_id', 'Partners'), } res_partner_category2()
related:	Sometimes you need to refer to the relation of a relation. For example, supposing you have objects: City -> State -> Country, and you need to refer to the Country from a City, you can define a field as below in the City object: 'country_id': fields.related( 'state_id', 'country_id', type="many2one", relation="res.country", string="Country", store=False) Where: The first set of parameters are the chain of reference fields to follow, with the desired field at the end. type is the type of that desired field. Use relation if the desired field is still some kind of reference. relation is the table to look up that reference in.