QUESTION: What is the purpose of the cross-referencing design? [signinlocker] SOLUTION The cross-referencing design is an alternative modeling approach that guarantees the absence of null values in the foreign key. It entails the creation of a relation schema to represent the relationship type. [/signinlocker]
QUESTION: What is the difference between the referencing relation schema and the referenced relation schema? How are these terms incorporated into the foreign key design? [signinlocker] SOLUTION The parent is the referenced relation schema and the child is the referencing relation schema (i.e., it references the relation schema that contains the primary key)….
QUESTION: What is required to map a relationship type that exhibits a 1:n cardinality ratio? [signinlocker] SOLUTION Using the foreign key design, place the key (either the primary key or a candidate key) of the parent as a foreign key attribute of the child. [/signinlocker]
QUESTION: What would cause a relational schema for a database to contain more relation schemas than there are entity types? [signinlocker] SOLUTION This is somewhat of a trick question. A relational schema has the same number of relation schemas as there are entity types as long as the Fine-granular Design-Specific ER diagram serves…
QUESTION: What is a primary key? How do the properties of a primary key differ from those of a candidate key? [signinlocker] SOLUTION A primary key is a candidate key that in addition to having the uniqueness and irreducibility properties also satisfies the entity integrity constraint (i.e., a primary key cannot have a…
QUESTION: What is a candidate key? How does a candidate key differ from a superkey? [signinlocker] SOLUTION A candidate key is defined as a superkey with no proper subsets that are superkeys. A candidate key has two properties: the uniqueness property and the irreducibility property, whereas a superkey possesses only the uniqueness property….
QUESTION: What is the difference between a derived attribute and a stored attribute in terms of their representation in a relation schema? [signinlocker] SOLUTION Only stored attributes are captured in a relation schema. [/signinlocker]