Tag: Standard Query Language

DP-900, Microsoft Certification, SQL

Additional Practice Questions: Identify common Structured Query Language (SQL) statements – SQL JOIN Focused (DP-900 Exam Prep)

Practice Questions – SQL JOIN focused questions

Question 1

What is the purpose of a SQL JOIN?

A. To delete duplicate rows
B. To combine data from multiple tables
C. To sort query results
D. To filter columns

✅ Answer: B

Explanation:
JOIN is used to combine rows from two or more related tables.

Question 2

Which type of JOIN returns only matching rows from both tables?

A. LEFT JOIN
B. RIGHT JOIN
C. INNER JOIN
D. CROSS JOIN

✅ Answer: C

Explanation:
INNER JOIN returns only rows where there is a match in both tables.

Question 3

A LEFT JOIN returns:

A. Only matching rows
B. All rows from the right table only
C. All rows from the left table and matching rows from the right
D. Only non-matching rows

✅ Answer: C

Explanation:
LEFT JOIN keeps all rows from the left table, even if there is no match.

Question 4

What happens when there is no matching row in a RIGHT JOIN?

A. The row is removed
B. NULL values are returned for missing matches
C. The query fails
D. Only matched rows are shown

✅ Answer: B

Explanation:
Unmatched columns return NULL values.

Question 5

Which JOIN type returns all possible combinations of rows between two tables?

A. INNER JOIN
B. LEFT JOIN
C. CROSS JOIN
D. FULL JOIN

✅ Answer: C

Explanation:
CROSS JOIN produces a Cartesian product (all combinations).

Question 6

Which SQL clause is used to define how tables are related in a JOIN?

A. WHERE
B. GROUP BY
C. ON
D. ORDER BY

✅ Answer: C

Explanation:
The ON clause specifies the relationship between tables.

Question 7

Given two tables: Customers and Orders. Each customer may have multiple orders. Which JOIN is typically used to retrieve all customers and their orders?

A. INNER JOIN
B. LEFT JOIN
C. CROSS JOIN
D. SELF JOIN

✅ Answer: B

Explanation:
LEFT JOIN ensures all customers appear, even those without orders.

Question 8

What does an INNER JOIN exclude?

A. Duplicate rows
B. Non-matching rows
C. NULL values only
D. Primary keys

✅ Answer: B

Explanation:
INNER JOIN only returns rows with matching values in both tables.

Question 9

Which JOIN is MOST likely to return fewer rows than the original tables?

A. CROSS JOIN
B. INNER JOIN
C. LEFT JOIN
D. FULL OUTER JOIN

✅ Answer: B

Explanation:
INNER JOIN returns only matches, often reducing row count.

Question 10

Which statement best describes a FULL OUTER JOIN?

A. Returns only matching rows
B. Returns all rows from both tables, matching where possible
C. Returns only left table rows
D. Returns only right table rows

✅ Answer: B

Explanation:
FULL OUTER JOIN returns all rows from both tables, with NULLs where no match exists.

✅ Quick Exam Takeaways

For DP-900 JOINs, remember:

✔ JOIN = combine related tables
✔ INNER JOIN = only matches
✔ LEFT JOIN = all left + matches
✔ RIGHT JOIN = all right + matches
✔ CROSS JOIN = all combinations
✔ ON clause defines relationships
✔ Unmatched values become NULL

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