How is the best way to restrict a delete on an item if it has a value in a many-to-many mapping?
For example: I have three tables: User, Group, and UserGroup. UserGroup is a many- to-many mapping table between User and Group. User has a relation called 'groups' and Group has a relation called 'users'. Pretty simple schema. I want the ability to delete a group, but only if it is not used by a user in which case I want it to fail. If I do 'session.delete(group)' it removes all the items in UserGroup so that it will always succeed. One obvious solution is to always check the length of the 'users' attribute whenever I want to remove a group. Is there a more generic way to do this that I can specify at the mapper level? -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
