Authentic WGU Certification Exam Data-Management-Foundations Questions Answers

Asimple primary keyconsists ofonly one columnthat uniquely identifies each row in a table.

Example Usage:

sql

CREATE TABLE Students (

StudentID INT PRIMARY KEY,

Name VARCHAR(50)

);

StudentIDis asimple primary keybecause it consists of only one field.

Why Other Options Are Incorrect:

Option B (Partition) (Incorrect):Refers topartitioned tables, which divide data for performance reasons butare not related to primary keys.

Option C (Stable) (Incorrect):This is not a recognized term in database keys.

Option D (Meaningless) (Incorrect):Primary keys are oftenmeaningless (e.g., auto-incremented IDs), but this isnot a term used to describe their structure.

Thus, the correct answer isSimple, as asingle-field primary keyis referred to as asimple primary key.

In SQL,literalsrepresent explicit values such asnumbers, strings, or binary datadirectly written into queries. For example:

SELECT * FROM Employees WHERE Salary > 50000;

Here, 50000 is anumeric literal.

Option A (Correct):Literalsare explicit values used in SQL queries, such as 123, 'John Doe', and TRUE.

Option B (Incorrect):Commentsare non-executable text used for documentation within SQL code, typically denoted by -- or /* ... */.

Option C (Incorrect):Identifiersare names oftables, columns, or other database objects, such as EmployeeID.

Option D (Incorrect):Keywordsare reserved words in SQL (e.g., SELECT, FROM, WHERE) that define operations and syntax.

TheALTER TABLEstatement is used to modify an existing database table structure. One common clause isCHANGE, which allows renaming a column and modifying its data type.

Example:

sql

ALTER TABLE Employees CHANGE COLUMN OldName NewName VARCHAR(50);

Option A (Incorrect):DELETE is used to removerows, not alter table structure.

Option B (Correct):CHANGE is avalid clausefor renaming and modifying columns in MySQL and some other databases.

Option C (Incorrect):STOP is not a valid SQL keyword for altering tables.

Option D (Incorrect):AGGREGATE refers to functions like SUM() and AVG(), not table alterations.