LIMIT clause behavior in SQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this query with LIMIT?

Consider a table Employees with columns id and name. It has 5 rows with ids from 1 to 5.
What rows will this query return?

SELECT * FROM Employees ORDER BY id DESC LIMIT 3;

SQL

SELECT * FROM Employees ORDER BY id DESC LIMIT 3;

A Rows with ids 5, 4, 3

B Rows with ids 3, 4, 5

C Rows with ids 1, 2, 3

D Rows with ids 1, 5, 3

💡 Hint

LIMIT returns the first N rows after sorting.

The query orders rows by id descending (5 to 1) and then returns the first 3 rows, which are ids 5, 4, and 3.

🧠 Conceptual

intermediate

What happens if LIMIT is zero?

What will this query return?

SELECT * FROM Employees LIMIT 0;

A Raises a syntax error

B Returns all rows

C Returns one row

D Returns no rows

💡 Hint

Think about what limiting to zero means.

LIMIT 0 means the query returns zero rows, so the result set is empty.

📝 Syntax

advanced

Which query correctly uses LIMIT with OFFSET?

You want to skip the first 2 rows and get the next 3 rows from a table.
Which query is correct?

A SELECT * FROM Employees LIMIT 3 OFFSET 2;

B SELECT * FROM Employees OFFSET 2 LIMIT 3;

C SELECT * FROM Employees LIMIT 2, 3;

D SELECT * FROM Employees LIMIT 3, OFFSET 2;

💡 Hint

Standard SQL uses LIMIT then OFFSET.

The correct syntax is LIMIT followed by OFFSET. Option A uses this correctly.

❓ optimization

advanced

How does LIMIT improve query performance?

You have a large table with millions of rows. You only want to display the first 10 rows.
How does adding LIMIT 10 affect the query execution?

A It increases query time because of extra processing

B It scans the entire table then returns 10 rows

C It stops scanning after finding 10 rows, reducing work

D It causes the database to sort all rows before limiting

💡 Hint

Think about how databases can stop early when limited.

LIMIT allows the database to stop scanning once it finds enough rows, improving speed.

🔧 Debug

expert

Why does this query cause an error?

Given this query:

SELECT * FROM Employees LIMIT -5;

What error will it cause?

A Runtime error due to invalid offset

B Syntax error because LIMIT cannot be negative

C Returns zero rows

D Returns all rows ignoring the negative limit

💡 Hint

LIMIT expects a non-negative integer.

LIMIT with a negative number is invalid syntax and causes an error.

Practice

1. What does the LIMIT clause do in an SQL query?

easy

A. It restricts the number of rows returned by the query.

B. It sorts the rows in ascending order.

C. It groups rows based on a column.

D. It deletes rows from the table.

Solution

1. Step 1: Understand the purpose of LIMIT

   The LIMIT clause is used to restrict the number of rows returned by a query.

2. Step 2: Compare with other options

   Sorting is done by ORDER BY, grouping by GROUP BY, and deleting by DELETE statement, not LIMIT.

3. Final Answer:

   It restricts the number of rows returned by the query. -> Option A

4. Quick Check:

   LIMIT = restrict rows [OK]

Hint: LIMIT controls how many rows you get back [OK]

Common Mistakes:

• Confusing LIMIT with ORDER BY
• Thinking LIMIT deletes rows
• Mixing LIMIT with GROUP BY

2. Which of the following is the correct syntax to get the first 5 rows from a table named employees?

easy

A. SELECT * FROM employees LIMIT 5;

B. SELECT * FROM employees TOP 5;

C. SELECT * FROM employees FETCH FIRST 5 ROWS;

D. SELECT * FROM employees WHERE LIMIT = 5;

Solution

1. Step 1: Identify correct LIMIT syntax

   The standard SQL syntax to limit rows is using LIMIT followed by the number, e.g., LIMIT 5.

2. Step 2: Check other options

   TOP 5 is SQL Server syntax, FETCH FIRST 5 ROWS is standard SQL but typically requires 'ONLY', and WHERE LIMIT = 5 is invalid.

3. Final Answer:

   SELECT * FROM employees LIMIT 5; -> Option A

4. Quick Check:

   LIMIT 5 = first 5 rows [OK]

Hint: Use LIMIT number after FROM to restrict rows [OK]

Common Mistakes:

• Using TOP instead of LIMIT in standard SQL
• Misplacing LIMIT inside WHERE clause
• Using FETCH without OFFSET incorrectly

3. Given the table products with rows:
id | name
1 | Apple
2 | Banana
3 | Cherry
4 | Date
5 | Elderberry
What is the result of the query:
SELECT name FROM products ORDER BY id DESC LIMIT 3;?

medium

A. ["Apple", "Banana", "Cherry"]

B. ["Elderberry", "Date", "Cherry"]

C. ["Cherry", "Date", "Elderberry"]

D. ["Date", "Elderberry", "Cherry"]

Solution

1. Step 1: Understand ORDER BY id DESC

   Ordering by id descending means rows are sorted from highest id to lowest: 5,4,3,2,1.

2. Step 2: Apply LIMIT 3

   LIMIT 3 returns the first 3 rows after sorting: ids 5,4,3 which correspond to Elderberry, Date, Cherry.

3. Final Answer:

   ["Elderberry", "Date", "Cherry"] -> Option B

4. Quick Check:

   ORDER BY DESC + LIMIT 3 = top 3 highest ids [OK]

Hint: ORDER BY DESC then LIMIT gets top N rows [OK]

Common Mistakes:

• Ignoring ORDER BY and taking first rows as is
• Mixing ascending and descending order
• Confusing LIMIT number with offset

4. What is wrong with this query?
SELECT * FROM orders LIMIT;

medium

A. LIMIT only works with numeric columns.

B. LIMIT cannot be used without ORDER BY.

C. LIMIT must be placed before FROM clause.

D. LIMIT requires a number to specify how many rows to return.

Solution

1. Step 1: Check LIMIT syntax

   LIMIT must be followed by a number indicating how many rows to return.

2. Step 2: Validate other options

   LIMIT can be used without ORDER BY, it comes after FROM, and works on any query regardless of column types.

3. Final Answer:

   LIMIT requires a number to specify how many rows to return. -> Option D

4. Quick Check:

   LIMIT needs a number [OK]

Hint: Always put a number after LIMIT [OK]

Common Mistakes:

• Omitting the number after LIMIT
• Thinking ORDER BY is mandatory with LIMIT
• Placing LIMIT before FROM

5. You want to show page 3 of a product list, showing 10 products per page, ordered by price ascending. Which query correctly uses LIMIT and OFFSET to achieve this?

hard

A. SELECT * FROM products ORDER BY price ASC LIMIT 10 OFFSET 30;

B. SELECT * FROM products ORDER BY price ASC LIMIT 30 OFFSET 10;

C. SELECT * FROM products ORDER BY price ASC LIMIT 10 OFFSET 20;

D. SELECT * FROM products ORDER BY price ASC LIMIT 20 OFFSET 10;

Solution

1. Step 1: Calculate OFFSET for page 3 with 10 rows per page

   Page 1 shows rows 0-9, page 2 shows 10-19, so page 3 starts at offset 20.

2. Step 2: Use LIMIT 10 to get 10 rows for the page

   LIMIT 10 returns 10 rows starting from OFFSET 20.

3. Final Answer:

   SELECT * FROM products ORDER BY price ASC LIMIT 10 OFFSET 20; -> Option C

4. Quick Check:

   Page 3 offset = (3-1)*10 = 20 [OK]

Hint: OFFSET = (page-1)*rows, LIMIT = rows per page [OK]

Common Mistakes:

• Using wrong OFFSET calculation
• Mixing LIMIT and OFFSET values
• Forgetting ORDER BY for consistent paging