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WGU Data Management - Foundations Exam - Topic 2 Question 12 Discussion

Which type of join is demonstrated by the following query?sqlSELECT *FROM Make, ModelWHERE Make.ModelID = Model.ID;
C) EQUIJOIN
A) NON-EQUIJOIN
B) SELF JOIN
D) CROSS JOIN

WGU Data Management - Foundations Exam - Topic 2 Question 12 Discussion

Actual exam question for WGU's WGU Data Management - Foundations exam
Question #: 12
Topic #: 2
[All WGU Data Management - Foundations Questions]

Which type of join is demonstrated by the following query?

sql

SELECT *

FROM Make, Model

WHERE Make.ModelID = Model.ID;

Show Suggested Answer Hide Answer
Suggested Answer: C

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.


Contribute your Thoughts:

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India
7 hours ago
I’m confused because I thought CROSS JOINs didn’t have a WHERE clause, but I’m not completely confident about the definitions.
upvoted 0 times
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Arlene
5 days ago
This looks similar to a practice question we did where we had to identify joins, and I feel like EQUIJOIN is the right answer here.
upvoted 0 times
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Tabetha
11 days ago
I'm not entirely sure, but I remember something about NON-EQUIJOINs being used for conditions other than equality.
upvoted 0 times
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Jacqueline
16 days ago
I think this might be an EQUIJOIN since it uses the equality operator in the WHERE clause.
upvoted 0 times
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