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WGU Data Management – Foundations Exam 온라인 연습
최종 업데이트 시간: 2025년12월09일
당신은 온라인 연습 문제를 통해 WGU Data Management Foundations 시험지식에 대해 자신이 어떻게 알고 있는지 파악한 후 시험 참가 신청 여부를 결정할 수 있다.
시험을 100% 합격하고 시험 준비 시간을 35% 절약하기를 바라며 Data Management Foundations 덤프 (최신 실제 시험 문제)를 사용 선택하여 현재 최신 60개의 시험 문제와 답을 포함하십시오.
정답:
Explanation:
The ABS() function in SQL returns the absolute value of a given number, effectively measuring its distance from zero.
Example Usage:
sql
SELECT ABS(-50), ABS(50);
Result:
50|50
This function ensures that numbers are always positive, regardless of their original sign.
Why Other Options Are Incorrect:
Option A (CONCAT) (Incorrect): Used to combine strings (not numbers).
Option B (LOWER) (Incorrect): Converts text to lowercase, not numerical operations.
Option C (FROM) (Incorrect): Part of SELECT FROM queries, not a function.
Thus, the correct choice is ABS(), which computes the absolute value of a number.
Reference: SQL Numeric Functions.
정답:
Explanation:
The ORDER BY clause in SQL is used to sort query results in ascending (ASC) or descending (DESC) order.
Example Usage:
sql
SELECT Name, Salary FROM Employees ORDER BY Salary DESC; This retrieves all employees, sorted by salary in descending order.
Why Other Options Are Incorrect:
Option A (BETWEEN) (Incorrect): Used for filtering ranges but does not order results.
Option B (DISTINCT) (Incorrect): Removes duplicate rows but does not control order.
Option D (LIKE) (Incorrect): Used for pattern matching, not sorting.
Thus, ORDER BY is the correct choice for defining the sequence of query results.
Reference: SQL Sorting with ORDER BY.
정답:
Explanation:
The BETWEEN keyword in SQL is used to filter values within a specified range. It is particularly useful for numeric and date-based queries.
Syntax of BETWEEN:
sql
SELECT * FROM Employees WHERE Salary BETWEEN 50000 AND 100000; Retrieves all employees whose salary is between $50,000 and $100,000 (inclusive).
Why Other Options Are Incorrect:
Option A (LIKE) (Incorrect): Used for pattern matching with wildcards (%, _). Example:
sql
SELECT * FROM Customers WHERE Name LIKE 'A%';
Option B (IN) (Incorrect): Used to match a value in a specified set, but not a range. Example:
sql
SELECT * FROM Employees WHERE Department IN ('HR', 'Finance', 'IT');
Option C (OR) (Incorrect): Used for logical conditions, but does not check a range. Example:
sql
SELECT * FROM Products WHERE Price < 10 OR Price > 50;
Thus, the correct choice is BETWEEN for filtering values within a range.
Reference: SQL WHERE and BETWEEN operations.
정답:
Explanation:
When a VIEW is created in SQL, users may insert or update data through that view. However, if a row is inserted or updated in such a way that it violates the condition of the VIEW’s WHERE clause, it can lead to inconsistencies.
To prevent such unwanted modifications, SQL provides the WITH CHECK OPTION clause.
How WITH CHECK OPTION Works:
Ensures that any new data (INSERT/UPDATE) still fits within the defined constraints of the VIEW.
If a user tries to insert or update a row that would not appear in the VIEW, the operation is rejected.
Example:
sql
CREATE VIEW HighSalaryEmployees AS
SELECT * FROM Employees WHERE Salary > 50000
WITH CHECK OPTION;
Now, if someone attempts:
sql
INSERT INTO HighSalaryEmployees (ID, Name, Salary)
VALUES (101, 'Alice', 30000);
This fails because 30000 does not satisfy Salary > 50000.
Why Other Options Are Incorrect:
Option B (Incorrect): JOIN VIEWS is not a valid SQL clause.
Option C (Incorrect): MATERIALIZED VIEW refers to stored views in some databases, but it does not reject incorrect inserts/updates.
Option D (Incorrect): BASE TABLE refers to the original table from which a VIEW is created.
Thus, the correct answer is WITH CHECK OPTION, which ensures that only valid data modifications occur.
Reference: View restrictions in SQL.
정답:
Explanation:
This query performs a join operation where records from the Make table and Model table are combined based on the condition Make.ModelID = Model.ID. This condition tests for equality, which is the definition of an EQUIJOIN.
Types of Joins in SQL:
EQUIJOIN (Correct Answer):
Uses an equality operator (=) to match rows between tables.
Equivalent to an INNER JOIN ON condition.
Example:
sql
SELECT *
FROM Employees
JOIN Departments ON Employees.DeptID = Departments.ID;
NON-EQUIJOIN (Incorrect):
Uses comparison operators other than = (e.g., <, >, BETWEEN).
Example:
sql
SELECT *
FROM Employees e
JOIN Salaries s ON e.Salary > s.MedianSalary;
SELF JOIN (Incorrect):
A table is joined with itself using table aliases.
Example:
sql
SELECT e1.Name, e2.Name AS Manager
FROM Employees e1
JOIN Employees e2 ON e1.ManagerID = e2.ID;
CROSS JOIN (Incorrect):
Produces Cartesian product (each row from Table A combines with every row from Table B).
Example:
sql
SELECT *
FROM Employees
CROSS JOIN Departments;
Thus, since our given query uses an equality condition (=) to join two tables, it is an EQUIJOIN.
Reference: SQL Joins in relational databases.
정답:
Explanation:
The UNION keyword in SQL is used to combine the results of two or more SELECT queries into a single result set while removing duplicate rows.
Example:
sql
SELECT Name FROM Employees
UNION
SELECT Name FROM Managers;
Option A (Correct): UNION combines results from multiple queries into one set, removing duplicates.
Option B (Incorrect): MERGE is not a valid SQL keyword for combining result sets (it is used in some database systems for data merging).
Option C (Incorrect): INTEGRATE is not a SQL keyword.
Option D (Incorrect): CONSOLIDATE is not an SQL keyword.
Reference: SQL UNION and set operations.
정답:
Explanation:
When performing a JOIN operation in MySQL, the ON clause specifies the joining condition, defining which columns from both tables should be matched.
Example:
sql
SELECT Employees.Name, Departments.DepartmentName FROM Employees
JOIN Departments ON Employees.DepartmentID = Departments.ID;
Option A (Incorrect): AS is used for aliasing tables and columns, not for specifying join conditions.
Option B (Incorrect): JOIN defines the type of join (INNER JOIN, LEFT JOIN, etc.), but does not specify the columns.
Option C (Correct): The ON clause is used to specify the join condition between two tables.
Option D (Incorrect): AND is used in filtering conditions, not for joining tables.
Reference: MySQL JOIN operations.
정답:
Explanation:
Non-relational databases (also called NoSQL databases) are designed for handling big data and unstructured data efficiently. They are optimized for horizontal scaling, making them ideal for large-scale distributed systems.
Option A (Correct): Non-relational databases are optimized for big data, handling massive volumes of data across distributed architectures.
Option B (Incorrect): NoSQL databases do not use SQL as their primary query language. They often use JSON-based queries (e.g., MongoDB).
Option C (Incorrect): Transaction-heavy applications require ACID compliance, which relational databases (SQL) handle better than NoSQL databases.
Option D (Incorrect): NoSQL databases use document, key-value, graph, or column-family storage models, not tables, columns, and rows like relational databases.
Reference: Characteristics of NoSQL databases.
정답:
Explanation:
In SQL syntax, the FROM clause is the first clause that follows SELECT. It specifies the table(s) from which the data will be retrieved.
Example:
sql
SELECT name, salary FROM Employees;
Option A (Correct): The FROM clause immediately follows the SELECT clause in MySQL.
Option B (Incorrect): VALUE is not a valid clause in MySQL SELECT statements.
Option C (Incorrect): WHERE is used to filter records after specifying the table in FROM.
Option D (Incorrect): TABLE is not a valid clause following SELECT in SQL.
Reference: MySQL SELECT statement structure.
정답:
Explanation:
The % operator in MySQL is known as the modulus operator. It returns the remainder of a division operation between two numbers.
Example:
sql
SELECT 10 % 3; -- Output: 1 (10 divided by 3 gives remainder 1)
Option A (Incorrect): Raising a number to a power is done using the POW() function or ^ in some SQL dialects.
Option B (Incorrect): The = operator is used for equality comparisons, not %.
Option C (Correct): The modulus operator (%) finds the remainder when one number is divided by another.
Option D (Incorrect): Subtraction is performed using the - operator.
Reference: MySQL arithmetic operators.
정답:
Explanation:
In MySQL, the BIGINT data type is a 64-bit integer that requires 8 bytes (64 bits) of storage. It is used to store large numerical values beyond the range of INT (4 bytes).
Option A (Incorrect): 1 byte corresponds to TINYINT, which can store values from -128 to 127.
Option B (Incorrect): 3 bytes is not a standard integer storage size in MySQL.
Option C (Incorrect): 4 bytes corresponds to INT, which has a range of -2,147,483,648 to 2,147,483,647.
Option D (Correct): BIGINT takes 8 bytes and supports a massive range of numbers from -2^63 to 2^63 -1.
Reference: MySQL data types and storage requirements.
정답:
Explanation:
The ALTER TABLE statement is used to modify an existing database table structure. One common clause is CHANGE, 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 remove rows, not alter table structure.
Option B (Correct): CHANGE is a valid clause for 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.
Reference: SQL ALTER TABLE syntax in SE 3050 zyBooks.
정답:
Explanation:
In SQL, literals represent explicit values such as numbers, strings, or binary data directly written into queries. For example:
SELECT * FROM Employees WHERE Salary > 50000;
Here, 50000 is a numeric literal.
Option A (Correct): Literals are explicit values used in SQL queries, such as 123, 'John Doe', and TRUE.
Option B (Incorrect): Comments are non-executable text used for documentation within SQL code, typically denoted by -- or /* ... */.
Option C (Incorrect): Identifiers are names of tables, columns, or other database objects, such as Employee ID.
Option D (Incorrect): Keywords are reserved words in SQL (e.g., SELECT, FROM, WHERE) that define operations and syntax.
Reference: SQL syntax fundamentals in SE 3050 zyBooks.
정답:
Explanation:
A query processor is responsible for query optimization and execution in a database management system (DBMS). It analyzes SQL statements, optimizes execution plans, and ensures efficient retrieval of data.
Option A (Correct): The query processor optimizes queries by analyzing metadata from the system catalog to determine the best execution strategy.
Option B (Incorrect): Logging transactions before applying changes is the responsibility of the transaction manager.
Option C (Incorrect): Translating instructions into file system commands is handled by the storage manager, not the query processor.
Option D (Incorrect): While the query processor helps retrieve results, the database engine and API layer are responsible for returning results to applications.
Reference: Query optimization and execution in relational databases.
정답:
Explanation:
Databases need to support Application Programming Interfaces (APIs) to enable seamless integration with general-purpose programming languages like Python, Java, and C#. APIs like ODBC (Open Database Connectivity) and JDBC (Java Database Connectivity) allow applications to interact with databases without requiring complex SQL commands.
Option A (Incorrect): The storage manager is responsible for managing low-level file system operations, but it does not simplify SQL integration with programming languages.
Option B (Incorrect): The ability to reverse results (e.g., using ORDER BY DESC) is a SQL feature but is unrelated to integration with programming languages.
Option C (Incorrect): The query processor optimizes and executes SQL queries but does not provide an interface for application development.
Option D (Correct): APIs allow databases to be accessed easily from different programming environments, simplifying integration.
Reference: Database connectivity using APIs in SE 3050 zyBooks.