Similarly, you may ask, what is overlapping in database?
Overlapping subtype: Non-unique subsets of the supertype entity set are called as overlapping subtype. Each entity instance of the supertype may appear at least one subtype. This rule specified with the letter “o” inside the circle is connected between the supertype and its subtypes.
Secondly, what is a disjoint subtype? Disjoint subtypes, also known as nonoverlapping subtypes, are subtypes that contain a unique subset of the supertype entity set; in other words, each entity instance of the supertype can appear in only one of the subtypes.
Also asked, what is the purpose of a subtype discriminator?
A subtype discriminator is the attribute in the supertype entity that is used to determine to which entity subtypethe supertype occurrence is related. For any given supertype occurrence, the value of the subtype discriminatorwill determine which subtype the supertype occurrence is related to.
What is the difference between partial completeness and total completeness?
Partial completeness means that some supertype occurrences might not be members of any subtype. Total completeness means that every supertype occurrence must be a member of at least one subtype.