10514931
Description
Flashcards by Tramaine Wanzo, updated more than 1 year ago
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Created by Tramaine Wanzo
about 7 years ago
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| Question | Answer |
| Subtype | is a subgrouping of the entities in an entity type that has attributes distinct form those in other subgrouping |
| Supertype | is an entity type that has one or more subtypes |
| Attribute Inheritance | Subtype entities inherit values of all attributes of the supertype |
| Relationship Inheritance | Subtype entities inherit values of all attributes of the supertype |
| Total Specialization Rule | Each entity instance of the super type MUST be an instance of some subtype |
| Partial Specialization Rule | An entity instance of the super type is allowed NOT to belong to any subtype |
| Disjoint Rule | An instance of the super type can by only ONE of the subtypes |
| Overlap Rule | An instance of the supertype could be more than one of the subtypes |
| Generalization | The process of first defining the more specialized entity types ( subtype) and then defining a more general entity type (supertype) from the subtypes. BOTTOM-UP |
| Specialization | The process of first defining the (Supertype) and then defining one of more (subtype) of the supertype. TOP-DOWN |
| Subtype Discriminations | is an attribute of the super type whose values determine the target subtypes |
| Disjoint | a ( simple attribute) with alternative values to indicate the possible subtypes |
| Overlapping | a ( composite ) attribute whose subparts pertain to different subtypes. Each subpart contains a boolean value to indicate whether or not the instance belongs to the associated subtype. |
| Entity | A person, place, an object, an event or concept about which the organization wishes to maintain data is called a/an Entity |
| Strong entity | exist ( independently ) or other types of entities has its own ( unique) identifier Entity box has ( single-line) |
| Weak entity | dependent on a ( strong entity) cannot exist on its own does not have a ( unique) identifier Entity box has (double-line) |
| Relationship | is an associations representing an interaction among entities that is of interest to the organization |
| Degree of a relationship | is the number of entity types that participate in it |
| Unary relationship | is a relationship between instances of a single entity type |
| Binary relationship | is a relationship between the instances of two entity types |
| Ternary relationship | is a simultaneous relationship among the instances of three entity types |
| cardinality constraints of a relationship | is the number of instances of one entity that can or must be associated with each instance of another entity |
| minimum cardinality | is the minimum number of instances of one entity that may be associated with each instance of another entity |
| maximum cardinality | is the maximum number o instances of one entity that may be associated with each instance of another entity |
| associative entity | A many-to-many relationship with attributes can be converted to an associative entity |
| Ternary relationships | a ternary relationship is a simultaneous relationship among instances of (three) entity types and should be converged to an ( associative entity) |
| attribute | is a property or characteristic of an entity that is of interest to the organization |
| Optional attribute | is an attribute that may not have a value for every entity instance |
| Multivalued attribute | is an attribute that can be broken down into meaningful component parts ( detailed attributes) |
| Composite attribute | is an attribute that may take on more than one value for a given entity instance |
| Derived attribute | is an attribute whose values can be calculated attribute values |
| Identifier | is an attribute ( or combinations of attributes) whose value distinguishes instances of an entity type |
| Logically | A database is an organized collection of (logically) related data |
| Metadata | Data that describe the properties of other data are ( Metadata) |
| DBMS, Database Management System | A software system that is used to create, maintain, and provide controlled access to user databases is called a/an ( DBMS, Database Management System) |
| The five phases of database development is: | Conceptual data modeling, logical database design, physical database design, implementation, and maintenance. |
| An Entity-relationship Model (E-R model) | An entity-relationship model ( E-R model) is a logical representation of the data for an organization or for a business area |
| primary key | an attribute or a combination of attributes that uniquely identifies each row in a relation Corresponds with the identifier of an (normal) entity type Simple key / composite key Guarantees that all rows are unique |
| Foreign key | an attribute or a combination of attributes that serves as the primary key of another relation in the database Represents the relationship between two relations |
| Domain Constraints | enforced by domain definitions which specify the allowable values for an attribute |
| Entity integrity | No primary key attribute may be null. All primary key fields MUST have data. |
| Referential integrity | any foreign key value MUST match a primary value in the relation of the one side (Or the foreign key can be null, if allowed) |
| one-to-many relationship (Map Binary Relationships to Relations) | Primary key on the one side becomes a foreign key on the many side |
| Many-to-Many relationship (Map Binary Relationships to Relations) | Create a NEW RELATION with the primary keys of the two entities as its primary key |
| One-to-one relationship (Map Binary Relationships to relations) | Primary key on the mandatory side becomes a foreign key on the optional side |
| Referential Integrity constraint | a rule maintains consistency among rows of two relations: any foreign key value MUST match a primary key value in the relation of the one side (Or the foreign key can be null, if allowed) |
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