388 Test 1: Short Answer Qs

What is the difference between data and information?

Data is raw, recorded facts, while information is data placed in context. Information makes the data meaningful.

In the DIKW pyramid, what changes as you move upward from Data to Information to Knowledge to Wisdom?

Value increases as context and understanding increase at each level.

What are two major problems caused by file-based storage when multiple applications share data?

Data redundancy and data inconsistency.

What is program-data dependency, and why is it harmful?

Program-data dependency, also called brittle coupling, occurs when file formats are built into application code. Changing the record layout may require editing and retesting every program that uses the file.

What was the major shift introduced by the relational model?

The relational model represents data as tables instead of pointer-based structures and allows users to specify what data they want. Tables are connected by keys.

What is the object-relational impedance mismatch?

It is the translation burden or friction involved in converting object graphs into rows and foreign keys and then rebuilding them into objects in code.

What are the three V's modern data systems must handle?

Volume, velocity, and variety.

What are three core services a DBMS provides that file systems usually do not?

Centralized data and schema management, integrity constraints, and data independence.

What is the main purpose of ER modeling?

To capture data requirements and business rules before implementation.

What are the three core building blocks of an ERD?

Entities, attributes, and relationships.

In database terms, what does an entity usually become in a relational database?

An entity becomes a table, and each instance of that entity becomes a row.

What is a strong (regular) entity?

A strong entity can be uniquely identified by its own attributes and can exist independently. It has its own primary key.

What is a weak entity, and how is it typically identified?

A weak entity cannot be uniquely identified by its own attributes alone and depends on an owner entity. Its key is typically formed by combining the owner's primary key with the weak entity's partial key.

What is a multi-valued attribute, and how is it typically implemented in a relational database?

A multi-valued attribute can have multiple values for a single entity instance. It is typically implemented as a separate table rather than storing a list in one column.

What is a derived attribute, and why might you avoid storing it?

A derived attribute is computed from other stored attributes. It may be avoided because storing a value that can be reliably calculated creates unnecessary redundancy and can cause inconsistency.

Why can't a many-to-many relationship be implemented directly in a relational database?

A many-to-many relationship requires an associative or junction table that converts the M:N relationship into two 1:M relationships.

In Crow's Foot notation, what do O, |, and the crow's foot mean?

O means zero or optional, | means one, and the crow's foot means many.

What problem does the relational model solve that a spreadsheet does not?

A spreadsheet is primarily a grid of data, while the relational model provides a shared, structured, and enforceable system of records with defined relationships and integrity rules.

Define table (relation), row (tuple), and column (attribute).

A table stores data about one type of entity. A row is one stored record or instance of that entity. A column represents one attribute or property of the entity.

What does "atomic values" mean in relational design, and why does it matter?

An atomic value is a single value rather than a list of multiple values in one cell. This keeps data structured and supports proper relational design.

What two properties must a primary key satisfy under entity integrity?

A primary key must be unique and cannot be NULL.

When do you use a composite primary key, and what is a common example?

A composite primary key is used when multiple columns together uniquely identify a row. A common example is a junction or associative table representing a many-to-many relationship.

What is a foreign key really doing: acting as a pointer or storing a copy?

A foreign key stores a copy of a key value from a referenced table, but it logically functions as a pointer to the related row.

What is referential integrity, and what problem does it prevent?

Referential integrity keeps relationships between tables valid by ensuring that a foreign key value references an existing key in the related table. It prevents invalid or orphaned references.

What are the three layers of consistency, or integrity constraints?

Domain constraints, entity integrity, and referential integrity.

How do you map an M:N relationship, and why is the junction table necessary?

Create a junction or associative table containing foreign keys that reference the primary keys of the two related tables. The junction table is necessary because multiple related values should not be stored as a list in a single column.