Chapter 6A - Relational Databases and Integrity

Hierarchical Database Model

A database model in which records follow one defined parent-child tree structure. Clue words: tree, one parent, parent-child. Example: each child record is organized beneath a single parent path. Fill-in: A parent-child tree is the ______ model. Answer: hierarchical.

Network Database Model

A navigational database model in which records may have multiple parent and child links. Clue words: navigational, multiple links, many parent paths. Example: a record can connect to more than one parent record. Fill-in: Multiple parent-child links describe the ______ model. Answer: network.

Relational Database Model

A database model that stores data in two-dimensional tables connected through primary and foreign keys. Clue words: tables, rows, columns, relationships, flexible queries. Example: Customer, Sale, and Cash Receipt tables are linked with keys. Fill-in: The model based on related tables is the ______ model. Answer: relational.

Advantages of Relational Databases

Relational databases are understandable, flexible for reporting and queries, and able to reduce duplicate storage through shared keyed tables. Clue words: two-dimensional tables, ad hoc queries, shared customer record. Example: Sales and Service use one authoritative Customer table. Fill-in: The relational model supports flexible ______ and reporting. Answer: queries.

Scalability

A database's ability to handle increasing data volume, users, or transaction demands while maintaining performance. Clue words: 10,000 to 50 million rows, growth, performance. Example: a database growing to 50 million rows requires scalable design. Fill-in: Handling large growth in data volume is ______. Answer: scalability.

Database Administrator (DBA)

A person responsible for database design, implementation, maintenance, access, repair, security, and performance. Clue words: database security, access, repair, implementation. Example: the DBA manages user access and database recovery. Fill-in: The professional responsible for a database is the ______. Answer: DBA.

Entity Integrity

Each table must have a primary key that is unique and non-null, so every row can be identified. Clue words: null PK, duplicate PK, missing primary key. Example: a Customer row with a null Customer ID violates entity integrity. Fill-in: Unique, non-null primary keys support ______ integrity. Answer: entity.

Referential Integrity

A foreign key value must match an existing primary-key value in the related table, unless the relationship is optional and the FK may be null. Clue words: Order Customer ID missing from Customer table, invalid child row. Example: Order Customer ID C-900 cannot exist unless Customer C-900 exists. Fill-in: Matching foreign keys to existing primary keys supports ______ integrity. Answer: referential.

Optional Foreign Key

A foreign key may be null when the relationship is optional and the database design permits no related record. Clue words: optional relationship, null Customer ID allowed. Example: an Order row may have a null Customer ID if the customer relationship is optional. Fill-in: A foreign key can be blank when the relationship is ______. Answer: optional.

Data Type

A rule specifying the kind of data a field can contain, such as number, text, date, or currency. Clue words: Amount field contains text, field type. Example: an Amount field should not contain the text “unknown.” Fill-in: A field containing the wrong kind of value violates its ______ requirement. Answer: data type.

Single-Valued Attribute

A relational table field should contain one value for each record, not multiple repeating values. Clue words: three phone numbers in one field, multivalued cell. Example: storing three phone numbers in one Phone field violates the single-valued attribute requirement. Fill-in: A field should contain one ______ per row. Answer: value.

Attribute Placement

Nonkey attributes should describe the class/table in which they are stored. Clue words: salary in Sales table, describes another entity. Example: Employee Salary belongs in Employee, not Sales. Fill-in: A nonkey attribute should describe its own ______. Answer: class.

Update Anomaly

A problem caused by storing the same fact in multiple places, requiring multiple updates and risking inconsistent data. Clue words: duplicate address, update every transaction table. Example: storing a customer's address once in Customer reduces update anomalies. Fill-in: Duplicate storage can create an update ______. Answer: anomaly.

Composite Primary Key

A primary key using more than one field, appropriate when the combination uniquely identifies a record. Clue words: Order ID plus Product ID, line item. Example: Order ID and Product ID together identify a line-item row. Fill-in: A key with two fields can be a ______ primary key. Answer: composite.