WGU Data Management - Foundations (D426) Exam Questions

The CHECK constraint is used in SQL to enforce rules on a column's values. It ensures that data inserted into a table meets specified conditions, such as range restrictions or logical rules.

Example Usage:

sql

CREATE TABLE Employees (

ID INT PRIMARY KEY,

Name VARCHAR(50),

Salary INT CHECK (Salary BETWEEN 30000 AND 150000)

);

This constraint ensures that salary values fall between 30,000 and 150,000.

If an INSERT or UPDATE statement tries to set Salary = 20000, it fails because it does not meet the CHECK condition.

Why Other Options Are Incorrect:

Option B (FROM) (Incorrect): Used in SELECT statements, not for constraints.

Option C (WHERE) (Incorrect): Filters rows in queries but does not enforce constraints.

Option D (SET) (Incorrect): Used for updating records (UPDATE table_name SET column = value) but not for defining constraints.

Thus, CHECK is the correct answer, as it ensures that column values remain within an expected range.

A valid SELECT statement in SQL follows this basic syntax:

sql

SELECT column1, column2

FROM table_name

WHERE condition;

The correct option D follows this syntax correctly.

Why Other Options Are Incorrect:

Option A (Incorrect): SQL does not use double quotes (') around column/table names unless explicitly required in some databases.

Option B (Incorrect): The WHERE clause must appear after the FROM clause.

Option C (Incorrect): ALL is not a valid keyword in standard SQL queries.

Thus, Option D follows the correct SQL syntax.

The logical design phase in database development focuses on structuring data efficiently to eliminate redundancy and ensure integrity. The final step in logical design is to apply normalization (normal forms) to optimize the database schema.

Steps in Logical Database Design:

Discover entities Identify real-world objects (e.g., Customers, Orders).

Determine cardinality Define relationships between entities (one-to-one, one-to-many).

Analyze data requirements Determine the attributes each entity needs.

Apply normal forms Eliminate redundancy and improve data consistency.

Example Usage:

After identifying entities like Students and Courses, applying 3rd Normal Form (3NF) ensures that data is organized without redundancy.

Why Other Options Are Incorrect:

Option A (Analyze data requirements) (Incorrect): Done earlier to define attributes.

Option C (Determine cardinality) (Incorrect): Done before normalization to establish relationships.

Option D (Discover entities) (Incorrect): Done at the beginning of database design.

Thus, the correct answer is Apply a normal form, as normalization is the last step in logical design.

In database design, an entity is classified as strong or weak based on whether it has a primary key that uniquely identifies its records.

Differences Between Strong and Weak Entities:

CREATE TABLE Orders (

OrderID INT PRIMARY KEY,

CustomerID INT

);

CREATE TABLE OrderDetails (

OrderDetailID INT,

OrderID INT,

ProductID INT,

PRIMARY KEY (OrderDetailID, OrderID),

FOREIGN KEY (OrderID) REFERENCES Orders(OrderID)

);

Orders is a strong entity (has OrderID as its own primary key).

OrderDetails is a weak entity (depends on OrderID for uniqueness).

Why Other Options Are Incorrect:

Option A (Association) (Incorrect): Associations describe relationships but do not define strong/weak entities.

Option C (Foreign key) (Incorrect): Weak entities depend on foreign keys, but primary keys define their status.

Option D (Cardinality) (Incorrect): Cardinality defines relationship constraints but does not differentiate entity types.

Thus, the correct answer is Primary key, as it is the defining characteristic between strong and weak entities.

In database design, attributes of an entity become columns in a relational table.

Example Usage:

For an Employee entity, attributes might include:

CREATE TABLE Employees (

EmployeeID INT PRIMARY KEY,

Name VARCHAR(50),

Salary DECIMAL(10,2),

DepartmentID INT

);

Each attribute (e.g., Name, Salary) becomes a column in the table.

Why Other Options Are Incorrect:

Option A (Modality) (Incorrect): Describes optional vs. mandatory relationships, not table structure.

Option B (Uniqueness) (Incorrect): Ensures distinct values but is not a column property.

Option D (Non-null values) (Incorrect): Ensures that columns must contain data but does not define attributes.

Thus, the correct answer is Attribute, as attributes of entities become table columns.