LIMIT and OFFSET for pagination in MySQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What rows does this query return?

Consider a table Employees with 10 rows ordered by id ascending. What rows does this query return?

SELECT * FROM Employees ORDER BY id LIMIT 3 OFFSET 4;

MySQL

SELECT * FROM Employees ORDER BY id LIMIT 3 OFFSET 4;

A Rows with id 5, 6, 7

B Rows with id 4, 5, 6

C Rows with id 1, 2, 3

D Rows with id 7, 8, 9

💡 Hint

OFFSET skips the first N rows, LIMIT picks how many rows after that.

OFFSET 4 skips first 4 rows (id 1 to 4), then LIMIT 3 picks next 3 rows (id 5, 6, 7).

📝 Syntax

intermediate

Which query has correct syntax for pagination?

Which of these queries correctly uses LIMIT and OFFSET in MySQL to get 5 rows starting from the 10th row?

A SELECT * FROM Products LIMIT 5 OFFSET 10;

B SELECT * FROM Products LIMIT 10, 5;

C SELECT * FROM Products OFFSET 10 LIMIT 5;

D SELECT * FROM Products LIMIT 5, OFFSET 10;

💡 Hint

MySQL supports two LIMIT syntaxes: LIMIT count OFFSET skip or LIMIT skip,count.

Option A uses LIMIT 5 OFFSET 10 which is valid syntax. Option A uses LIMIT 10,5 which means skip 10, take 5, and is also valid in MySQL. But since the question asks for correct syntax to get 5 rows starting from 10th row, option A is preferred as it is clearer. Option A and D are invalid syntax.

❓ optimization

advanced

How to optimize pagination for large OFFSET values?

You have a table with millions of rows. Using LIMIT 10 OFFSET 1000000 is slow. Which approach improves performance for pagination?

A Remove ORDER BY clause to speed up query.

B Increase OFFSET value to skip more rows.

C Use ORDER BY random() with LIMIT 10.

D Use WHERE clause with indexed column to filter rows after last seen id.

💡 Hint

OFFSET skips rows but still scans them internally, which is slow for large values.

Using WHERE with an indexed column (like id > last_seen_id) allows the database to jump directly to the needed rows without scanning all skipped rows. Increasing OFFSET just makes it slower. ORDER BY random() is very slow. Removing ORDER BY changes result order and may not be acceptable.

🧠 Conceptual

advanced

Why does OFFSET affect query performance?

Why does using a large OFFSET value in a query like SELECT * FROM table LIMIT 10 OFFSET 1000000 cause slow performance?

A Because LIMIT forces the database to sort all rows.

B Because OFFSET causes the database to lock all rows.

C Because the database must scan and discard all rows before the OFFSET.

D Because OFFSET disables use of indexes.

💡 Hint

Think about what OFFSET means internally for the database engine.

OFFSET tells the database to skip a number of rows, so it must scan and discard those rows before returning the requested rows. This scanning causes slow performance for large OFFSET values.

🔧 Debug

expert

Identify the error in this pagination query

This query is intended to return 10 rows starting from the 20th row, but it causes a syntax error:

SELECT * FROM Orders LIMIT OFFSET 20, 10;

What is the error?

A LIMIT must be a single number without OFFSET.

B The syntax should be LIMIT 10 OFFSET 20 without a comma.

C LIMIT and OFFSET are reversed; OFFSET should come after LIMIT with a number.

D OFFSET cannot be used with LIMIT in MySQL.

💡 Hint

Check the correct order and syntax of LIMIT and OFFSET in MySQL.

The query uses 'LIMIT OFFSET 20, 10' which is invalid syntax. The correct syntax is either 'LIMIT 10 OFFSET 20' or 'LIMIT 20, 10' (meaning OFFSET 20, LIMIT 10). The comma syntax does not use the word OFFSET.

Practice

1. What does the LIMIT clause do in a MySQL query?

easy

A. It controls how many rows the query returns.

B. It controls the order of the rows returned.

C. It filters rows based on a condition.

D. It changes the database schema.

Solution

1. Step 1: Understand the purpose of LIMIT

   The LIMIT clause restricts the number of rows returned by a query.

2. Step 2: Compare with other options

   Ordering is done by ORDER BY, filtering by WHERE, and schema changes by DDL commands, not LIMIT.

3. Final Answer:

   It controls how many rows the query returns. -> Option A

4. Quick Check:

   LIMIT = number of rows [OK]

Hint: LIMIT sets max rows returned, like page size [OK]

Common Mistakes:

• Confusing LIMIT with ORDER BY
• Thinking LIMIT filters rows by condition
• Assuming LIMIT changes table structure

2. Which of the following is the correct syntax using the OFFSET keyword to get 10 rows starting from the 7th row in MySQL?

easy

A. SELECT * FROM table LIMIT 6, 10;

B. SELECT * FROM table LIMIT 10 OFFSET 6;

C. SELECT * FROM table OFFSET 6 LIMIT 10;

D. SELECT * FROM table LIMIT 10, 6;

Solution

1. Step 1: Understand LIMIT and OFFSET syntax

   MySQL supports both LIMIT count OFFSET offset and LIMIT offset, count syntax.

2. Step 2: Identify correct syntax for 10 rows starting at 7th row

   OFFSET 6 means skip first 6 rows, then LIMIT 10 means get next 10 rows. SELECT * FROM table LIMIT 10 OFFSET 6; uses this correctly.

3. Final Answer:

   SELECT * FROM table LIMIT 10 OFFSET 6; -> Option B

4. Quick Check:

   LIMIT count OFFSET offset = correct syntax [OK]

Hint: Use LIMIT count OFFSET offset for clarity [OK]

Common Mistakes:

• Swapping LIMIT and OFFSET values
• Using OFFSET before LIMIT incorrectly
• Confusing LIMIT offset,count with LIMIT count OFFSET offset

3. Given the table users with rows numbered by id from 1 to 20, what rows will this query return?
SELECT * FROM users ORDER BY id ASC LIMIT 5 OFFSET 10;

medium

A. Rows with id 1 to 5

B. Rows with id 6 to 10

C. Rows with id 11 to 15

D. Rows with id 16 to 20

Solution

1. Step 1: Understand OFFSET and LIMIT effect on rows

   OFFSET 10 skips first 10 rows (id 1 to 10), LIMIT 5 returns next 5 rows.

2. Step 2: Identify which rows are returned

   After skipping 10 rows, rows with id 11 to 15 are returned.

3. Final Answer:

   Rows with id 11 to 15 -> Option C

4. Quick Check:

   OFFSET 10 + LIMIT 5 = rows 11-15 [OK]

Hint: OFFSET skips rows, LIMIT picks next rows [OK]

Common Mistakes:

• Counting OFFSET as inclusive row
• Mixing up OFFSET and LIMIT order
• Assuming OFFSET starts at 1 instead of 0

4. Identify the error in this query intended to get 5 rows starting from the 3rd row:
SELECT * FROM products LIMIT OFFSET 3, 5;

medium

A. Syntax error: LIMIT should come before OFFSET without comma.

B. OFFSET cannot be used with LIMIT in this way.

C. No error; query is correct.

D. LIMIT and OFFSET are reversed in order.

Solution

1. Step 1: Check correct syntax for LIMIT and OFFSET

   Correct syntax is either LIMIT count OFFSET offset or LIMIT offset, count without the word OFFSET in the second form.

2. Step 2: Identify error in given query

   The query uses both LIMIT and OFFSET keywords together incorrectly with a comma, causing syntax error.

3. Final Answer:

   Syntax error: LIMIT should come before OFFSET without comma. -> Option A

4. Quick Check:

   LIMIT offset,count or LIMIT count OFFSET offset [OK]

Hint: Use either LIMIT offset,count or LIMIT count OFFSET offset [OK]

Common Mistakes:

• Mixing LIMIT and OFFSET keywords with commas
• Using OFFSET before LIMIT
• Adding OFFSET keyword with comma syntax

5. You want to display page 4 of a product list, showing 15 products per page, ordered by created_at descending. Which query correctly uses LIMIT and OFFSET?

hard

A. SELECT * FROM products ORDER BY created_at DESC LIMIT 45 OFFSET 15;

B. SELECT * FROM products ORDER BY created_at DESC LIMIT 60 OFFSET 15;

C. SELECT * FROM products ORDER BY created_at DESC LIMIT 15, 45;

D. SELECT * FROM products ORDER BY created_at DESC LIMIT 15 OFFSET 45;

Solution

1. Step 1: Calculate OFFSET for page 4 with 15 items per page

   Page 1 shows rows 0-14, page 2 rows 15-29, page 3 rows 30-44, so page 4 starts at offset 45.

2. Step 2: Write query with LIMIT and OFFSET

   LIMIT 15 means 15 rows per page, OFFSET 45 skips first 45 rows. SELECT * FROM products ORDER BY created_at DESC LIMIT 15 OFFSET 45; matches this.

3. Final Answer:

   SELECT * FROM products ORDER BY created_at DESC LIMIT 15 OFFSET 45; -> Option D

4. Quick Check:

   OFFSET = (page-1)*page_size = 45 [OK]

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

Common Mistakes:

• Swapping LIMIT and OFFSET values
• Calculating OFFSET incorrectly
• Using LIMIT as total rows instead of per page