ANY and ALL with arrays in PostgreSQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Using ANY with array comparison

Given the table products with a column price and an array {100, 200, 300}, what does the following query return?

SELECT name FROM products WHERE price = ANY (ARRAY[100, 200, 300]);

A All products with price less than 100, 200, or 300

B All products with price exactly 100, 200, or 300

C All products with price greater than 100, 200, or 300

D No products, because the syntax is invalid

💡 Hint

ANY checks if the price matches any element in the array.

The = ANY operator compares the price to each element in the array and returns true if any match is found. So it selects products priced exactly 100, 200, or 300.

❓ query_result

intermediate

Using ALL with array comparison

What does this query return?

SELECT name FROM products WHERE price > ALL (ARRAY[50, 75, 90]);

A Products with price less than 50, 75, and 90

B Products with price greater than 50 or 75 or 90

C Products with price greater than 50, 75, and 90

D Syntax error due to ALL usage

💡 Hint

ALL means the condition must be true for every element in the array.

price > ALL means price must be greater than every element in the array, so price must be greater than 90 (the largest).

📝 Syntax

advanced

Identify the syntax error with ANY and arrays

Which option contains a syntax error when using ANY with arrays in PostgreSQL?

A SELECT * FROM orders WHERE quantity = ANY [10, 20, 30];

B SELECT * FROM orders WHERE quantity = ANY (ARRAY[10, 20, 30]);

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D SELECT * FROM orders WHERE quantity = ANY (ARRAY[10,20,30]);

💡 Hint

PostgreSQL requires ARRAY keyword and parentheses for arrays.

Option A uses square brackets without ARRAY keyword and parentheses, which is invalid syntax in PostgreSQL.

🧠 Conceptual

advanced

Understanding ALL with empty arrays

What is the result of this query if the array is empty?

SELECT * FROM products WHERE price > ALL (ARRAY[]::integer[]);

A Returns all rows because condition is true for all elements (none exist)

B Returns no rows because comparison fails

C Raises an error due to empty array

D Returns rows where price is NULL

💡 Hint

Think about how ALL behaves with no elements to compare.

ALL with an empty array always returns true because there is no element to contradict the condition, so all rows match.

❓ optimization

expert

Optimizing queries with ANY and large arrays

You have a large array of IDs and want to find matching rows in users table by id. Which query is most efficient?

A) SELECT * FROM users WHERE id = ANY (ARRAY[...large array...]);
B) SELECT * FROM users WHERE id IN (SELECT unnest(ARRAY[...large array...]));
C) SELECT * FROM users WHERE id = ANY (ARRAY[...large array...]) AND active = true;
D) SELECT * FROM users WHERE id IN (...large list of IDs...);

A Using = ANY with a large array directly

B Using IN with unnest of the array

C Using IN with a large list of IDs directly

D Using = ANY with array and extra filter active = true

💡 Hint

Adding filters can help the planner optimize the query better.

Option D allows the planner to use indexes on active and id together, improving performance over just matching ANY or IN with large arrays.