WGU Updated Data-Management-Foundations Exam Questions and Answers by osian

Indatabase design, an entity is classified asstrong or weakbased on whether it has aprimary keythat 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 astrong entity(has OrderID as its own primary key).

OrderDetails is aweak entity(depends on OrderID for uniqueness).

Why Other Options Are Incorrect:

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

Option C (Foreign key) (Incorrect):Weak entitiesdepend on foreign keys, butprimary keysdefine their status.

Option D (Cardinality) (Incorrect):Cardinality definesrelationship constraintsbut doesnot differentiate entity types.

Thus, the correct answer isPrimary key, as it is the defining characteristic betweenstrong and weak entities.

Analiasis used in SQL to give atemporaryname to a table or column within a query. It makes queries more readable and helps in cases where a table needs to be referenced multiple times (e.g., in aself-join).

Example Usage:

sql

SELECT e.Name, d.DepartmentName

FROM Employees AS e

JOIN Departments AS d

ON e.DeptID = d.ID;

Here,Employees is aliased as eandDepartments as d, making the query shorter and clearer.

Why Other Options Are Incorrect:

Option A (HAVING) (Incorrect):Used to filter grouped results, not create aliases.

Option B (NEW) (Incorrect):Not a valid SQL keyword for aliasing.

Option D (UNION) (Incorrect):Combines result sets but does not rename tables.

Thus, the correct answer isALIAS, which allows fortemporary naming of tables or columns.

Anindex scanis a database operation thatquickly locates table blocksusing anindexrather than scanning the entire table. It significantly improves query performance.

Example Usage:

sql

SELECT * FROM Employees WHERE EmployeeID = 105;

If EmployeeID isindexed, the database uses anindex scantoquickly find the record.

Why Other Options Are Incorrect:

Option A (Binary search) (Incorrect):A searching algorithm, but not a database operation.

Option B (Table scan) (Incorrect):Scans theentire table, which isslowerthan an index scan.

Option C (Fan-out) (Incorrect):Refers tobranching in B-Treesbut doesnot locate table blocks directly.

Thus, the correct answer isIndex scan, as it efficiently locates table blocks.