SQL Server Security understanding.

Any securable can only be owned by a unique owner. This owner can do anything for it. Only the owner can see this object in SSMs; a principal (user/role) the securable can be accessed even if it is not the owner of a securable. However, if it is not the owner, the securable cannot be seen in SSMs; when selecting the owner relationship, you cannot click it again. The reason is that any securable must have one owner. simply canceling the selection of one owner does not explicitly specify another owner, so it is not allowed; schema can use permission to specify various permissions for all dB objects in its Schema (granularity only to schema) for different principal; principal (user/role) you can use securables to set various permissions for each dB object in a DB object or some dB objects (through schema) (the granularity is the lowest dB object ); Distribution of objects to people:Securable uses permission to allocate principal permissions; People allocate things:Principal uses the owner and securables methods to control securable permissions; Securable and principal are both database-level concepts: securable = any dB objectsprincipal = user/rolelogin obtains the internal Permission Logic of the database by ing to the DB user;
PS: SQL Server permissions hierarchy (Database Engine): http://msdn.microsoft.com/en-us/library/ms191465.aspx