Chapter 8 (Section 1) Final Revision #1

A structured collection of data items that are accessible by various applications.

A database that links data items together via the use of internal pointers, where data is stored in different tables which are linked using primary and foreign keys.

A group of similar data organized into rows (for entities) and columns (for attributes).

A row in a table that represents a single instance of an entity.

A column/attribute in a table representing a specific data item or characteristic stored about an entity.

Anything about which data can be stored, such as a person, event, or object.

To optimize search operations by creating a structure for fast data retrieval based on specific columns.

A collection of data items structured as records, where each record contains fields about the same object.

• Duplicate data (redundancy). • Format inconsistency. • Inconsistent data across different files.

Duplicated data across multiple files wastes storage space and increases data redundancy.

• Flat-file has more data redundancy: the same data is stored many times (in relational, data is stored in different tables which are linked). • There is program-data dependence with flat-files: any changes to the structure of the data means the programs that access that data have to be re-written. • Flat-file has more data inconsistency // worse data integrity: duplicated data might be stored differently; when data is updated in one place, it is not updated everywhere. • It is not easy to perform complex searches/queries: a new program has to be written each time. • Flat files could have a lack of privacy: user views cannot easily be implemented.

• Reduced data redundancy // less repeated data: each item of data is only stored once because linked tables mean each data item is stored only once. • Maintains data consistency // improves data integrity: changes in one table will automatically update in another; linked data cannot be entered differently in two tables; only needs to be updated once. • Program-data independence: the data is separate from the software, so changes to the data do not require programs to be re-written. • Complex queries are easier to run. • Can provide different views: so users can only see specific aspects of the database.

The ability to perform diverse queries without being limited by the specific structure of the data or the software; data is separate from the software so structural changes do not require programs to be re-written.

Data changes are instantly available across all applications because information is stored only once, ensuring consistency.

• Adding new files. • Inserting/retrieving/updating data. • Cross-referencing data for analysis.

An attribute/field (or set of attributes/fields) that could be a primary key — the smallest set of attributes that can uniquely identify a record without duplication.

A candidate key is any attribute or set of attributes that could uniquely identify a record; the primary key is the specific candidate key selected by the designer to perform that role.

A unique identifier for a table selected from the available candidate keys.

An alternative unique identifier used for accessing records.

It serves as an alternative identifier for a record, used primarily to provide a different path for searching or indexing data without replacing the primary key.

A field/attribute in one table that is linked to a Primary Key in another table; it links records in one table to the primary key of another table.