Chapter 6/ Concepts of DataBase Management/ 8th Edition/ Phil Pratt ; Mary Last – Flashcards
Unlock all answers in this set
Unlock answersquestion
Artificial key
answer
A column created for an entity to serve solely as the primary key and that is visible to users.
question
Alternate Key
answer
A candidate key that was not chosen to be the primary key.
question
Bottom-up Design Method
answer
A design method in which specific user requirements are synthesized into a design. Design starts at a low level. Specific user requirements drive design process.
question
Cardinality
answer
The number of items that must be included in a relationship. * An entity in a relationship with a MINIMUM cardinality of ZERO, plays an OPTIONAL role in the relationship. *An entity with a MINIMUM cardinality of ONE plays a MANDATORY role in the relationship.
question
Category
answer
An IDEF1X name for an entity sub-type.
question
Complete Category
answer
An IDEF1X. A collection of subtypes with the property that every element of the supertype is an element of at least one subtype.
question
Composite Entity
answer
Exists to implement a many-to-many-relationship.
question
Cumulative Design
answer
Supports all the user views encountered during a design process.
question
DBDL (Database Design Language)
answer
A relational-like language that is used to represent the result of the database design process.
question
Dependent Entity
answer
An entity that requires a relationship to another entity for identification .
question
Entity-Relationship Model (ER Model)
answer
An approach to representing data in a database that uses ER diagrams exclusively as the tool for representing entities, attributes and relationships. Visually represents database structure. Rectangle represents each entity. Relationships are drawn as diamonds.
question
Entity Subtype
answer
Entity "A" is a subtype of entity "B" IF EVERY occurrence of entity "A" is ALSO an occurrence of entity "B." Table that is a subtype of another table.
question
Existence Dependency
answer
Existence of one entity depends on the existence of another related entity.
question
First Normal Form (1NF)
answer
Table does not contain multiple entries in a field for a single record.
question
IDEF1X
answer
A type of ER diagram; or technically a language of the IDEF (Integrated Definition) family of languages that is used for data modeling.
question
Identity Relationship
answer
A relationship that is necessary for identification of an entity.
question
Incomplete Category
answer
An IDEF1X; a collection of subtypes with the property that there are elements of the super type that are NOT elements of any subtype.
question
Independent Entity
answer
An entity that does not require a relationship to another entity for identification
question
Information-Level design
answer
The step during DB design in which the goal is to create a clean, DBMS independent design, that will support all user requirements. 1.) Represent the user view as a collection of tables * STEP 1: Determine the entities involved and create a separate table for each type of entry *STEP 2: Determine the primary key for each table *STEP 3: Determine the attributes/properties for each entity *STEP 4: Determine relationships between the entities ONE-TO-MANY/ MANY-TO-MANY/ ONE-TO-ONE 2.) Normalize these tables (3rd number form (3NF) the Primary Key) 3.) Identify all keys in these tables (primary, alternate, secondary, and foreign) 4.) Merge the results of Steps 1-3 into the cumulative design.
question
Intelligent Key
answer
A primary key that consists of a column or collection of columns that is an inherent characteristic of the entity. ALSO CALLED A LOGICAL KEY.
question
Logical Key
answer
A primary key that consists of a column or collection of columns that is an inherent characteristic of the entity. ALSO CALLED AN INTELLIGENT KEY.
question
Mandatory Role
answer
The role in a relationship played by an entity with a minimum cardinality of 1 (THAT IS, THERE MUST BE AT LEAST ONE OCCURRENCE OF THE ENTITY).
question
Many-to-Many Relationship
answer
A relationship between 2 entities in which each occurrence of each entity can be related to many occurrences of the other entity. *CREATE A NEW TABLE WHOSE PRIMARY KEY IS THE COMBINATION OF THE PRIMARY KEYS OF THE ORIGINAL TABLES *YOU CANNOT IMPLEMENT A M2M
question
Many-to-Many-to-Many Relationship
answer
A relationship between 3 entities in which each occurrence of each entity can be related to many occurrences of each of the other entities.
question
Natural Key
answer
Consists of a column that uniquely identifies an entity. Also called a logical key or an intelligent key.
question
Non-Identifying Relationship
answer
A relationship that is not necessary for identification.
question
Null
answer
Special value. Represents absence of a value in a field. Used when a vale is unknown or inapplicable.
question
One-To-Many Relationship
answer
A relationship between two entities in which EACH occurrence of the 1st entity is related to MANY occurrences of the 2nd entity, and EACH occurrence of the 2nd entity is related to at most, one occurrence of the 1st entity. *INCLUDES PRIMARY KEY OF THE "ONE" TABLE AS A FOREIGN KEY IN THE "MANY" TABLE
question
One-to-One Relationship
answer
A relationship between 2 entities in which each occurrence of the first entity is related to ONE occurrence of the 2nd entity AND each occurrence of the 2nd entity is related to, at most, one occurrence of the 1st entity. *SIMPLEST IMPLEMENTATION IS TO TREAT IT AS A ONE-TO-MANY RELATIONSHIP
question
Optional Rule
answer
The role in a relationship played by an entity with a minimum cardinality of ZERO (that is, there need not be any occurrences of the entity).
question
Physical-Level Design
answer
The step during DB design in which a design for a given DBMS is produced from the final information-level design. *Process consists of creating a table for each entity in the DBDL design.
question
Second Normal Form (2NF)
answer
Table is in 1NF and no monkey field depends on only a portion of the primary key.
question
Secondary Key
answer
A column (attribute) or collection of columns that is of interest for retrieval purposes (and that is not already designated as some other type of key).
question
Splitting Tables
answer
To avoid use of null values
question
Surrogate Key
answer
A system-generated primary key that is usually hidden from users. Also called a synthetic key.
question
Survey Form
answer
Used to collect information from users. Must contain particular elements; 1.) Entity Information 2.) Attribute (column) information 3.) Relationships 4.) Functional Dependencies 5.) Processing Information. *Useful for documenting the information gathered for database design process.
question
Synthetic Key
answer
A system-generated primary key that is usually hidden from users.
question
Top-Down Design Method
answer
A design method that begins with a general DB design that models the overall enterprise and then repeatedly refines the model to achieve a design that supports all necessary applications. Refines model until design supports all necessary applications.
question
Target/ Third normal Form
answer
Tabel is in 2NF and only a primary (candidate) key can determine another column.
question
User View
answer
Set of requirements necessary to support operations of a particular database user.
question
Weak Entity
answer
Depends on another entity for its own existence.
question
Database design is a two-part process
answer
*Information-Level Design (NOT dependent on a particular DBMS). *Physical-Level Design (appropriate for the particular DBMS being used). *Database design is represented in DBDL (Database Language Design). *Designs can be represented visually, using entity-relationship (E-R) diagrams.
question
To obtain information from existing documents:
answer
1.) List all attributes present in the document 2.) Identify potential functional dependencies 3.) Make a tentative list of tables 4.) Use the functional dependencies to refine the list
question
To implement a one-to-one relationship
answer
1.) Include primary key of one table in the other table as a foreign key and indicate the foreign key as an alternate key.
question
If a table's primary key consists of three (or more) columns:
answer
1.) Determine whether there are independent relationships between pairs of these columns.
question
If a table contains columns that can be null and the nulls mean that the column is inapplicable for some rows:
answer
You can split the table, placing the null column(s) in separate tables
question
The result of merging third normal form tables:
answer
May not be in third normal form
question
Entity-Relationship (ER) MODEL represents:
answer
The structure of a DB using and E-R DIAGRAM
