ALL, ANY, SOME with subqueries in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the ALL keyword do when used with a subquery in SQL?

ALL compares a value to every value returned by the subquery. The condition is true only if the comparison holds for all values.

beginner

How does ANY differ from ALL in SQL subqueries?

ANY checks if the condition is true for at least one value returned by the subquery. It returns true if any single value satisfies the condition.

beginner

What is the synonym of ANY in SQL when used with subqueries?

SOME is a synonym for ANY. Both work the same way and can be used interchangeably.

intermediate

Write a simple example of using ALL with a subquery to find employees with salary greater than all salaries in department 10.

SELECT employee_name FROM employees WHERE salary > ALL (SELECT salary FROM employees WHERE department_id = 10);

intermediate

Explain why salary > ANY (subquery) might return more rows than salary > ALL (subquery).

salary > ANY (subquery) returns true if salary is greater than at least one value in the subquery, so it matches more rows. salary > ALL (subquery) requires salary to be greater than every value, which is stricter and returns fewer rows.

Which keyword checks if a value is greater than every value returned by a subquery?

A ALL

B ANY

C SOME

D IN

ALL requires the condition to be true for every value returned by the subquery.

What does SOME mean in SQL when used with subqueries?

A Equivalent to EXISTS

B Equivalent to ALL

C Equivalent to IN

D Equivalent to ANY

SOME is a synonym for ANY, meaning the condition must be true for at least one value.

If you want to find rows where a value is less than at least one value in a subquery, which keyword do you use?

A ALL

B ANY

C NONE

D EXISTS

ANY checks if the condition is true for any single value returned by the subquery.

What will the query SELECT * FROM products WHERE price > ALL (SELECT price FROM products WHERE category = 'Books'); return?

A Products with price greater than every book price

B Products with price greater than some book price

C Products with price equal to any book price

D All products in the 'Books' category

The query returns products priced higher than all books, meaning strictly greater than every book price.

Which of these is NOT true about ANY and ALL?

A <code>ANY</code> returns true if condition matches at least one value

B <code>ALL</code> returns true if condition matches every value

C <code>ANY</code> and <code>ALL</code> are interchangeable

D <code>SOME</code> is a synonym for <code>ANY</code>

ANY and ALL have different meanings and are not interchangeable.

Explain how the ALL keyword works with subqueries in SQL and give a simple example.

Think about how a value compares to every value in a list.

Describe the difference between ANY and ALL when used with subqueries and when you might use each.

Consider how strict the condition is for each keyword.

Practice

1. What does the ALL keyword do in a PostgreSQL query with a subquery?

easy

A. Returns all rows from the main query regardless of the subquery.

B. Checks if a condition is true for at least one value returned by the subquery.

C. Checks if a condition is true for every value returned by the subquery.

D. Joins the main query with the subquery on matching columns.

Solution

1. Step 1: Understand the role of ALL

   The ALL keyword compares a value to every value returned by a subquery.

2. Step 2: Interpret the condition

   It returns true only if the condition holds for all values from the subquery.

3. Final Answer:

   Checks if a condition is true for every value returned by the subquery. -> Option C

4. Quick Check:

   ALL means every value must satisfy condition [OK]

Hint: ALL means every value must meet the condition [OK]

Common Mistakes:

• Confusing ALL with ANY or SOME
• Thinking ALL returns all rows without condition
• Assuming ALL works like a JOIN

2. Which of the following is the correct syntax to use ANY with a subquery in PostgreSQL?

easy

A. SELECT * FROM table WHERE column = ANY (SELECT col FROM othertable);

B. SELECT * FROM table WHERE column ANY = (SELECT col FROM othertable);

C. SELECT * FROM table WHERE ANY column = (SELECT col FROM othertable);

D. SELECT * FROM table WHERE column = (ANY SELECT col FROM othertable);

Solution

1. Step 1: Recall correct ANY syntax

   ANY is used as: column operator ANY (subquery), e.g., column = ANY (subquery).

2. Step 2: Check each option

   SELECT * FROM table WHERE column = ANY (SELECT col FROM othertable); matches correct syntax. Others have misplaced ANY or wrong order.

3. Final Answer:

   SELECT * FROM table WHERE column = ANY (SELECT col FROM othertable); -> Option A

4. Quick Check:

   ANY goes after operator and before subquery in parentheses [OK]

Hint: Use operator = ANY (subquery) syntax [OK]

Common Mistakes:

• Placing ANY before the column name
• Omitting parentheses around subquery
• Using ANY without an operator

3. Given the tables:
products(id, price)
and
discounts(min_price)
What does this query return?

SELECT id FROM products WHERE price > ALL (SELECT min_price FROM discounts);

medium

A. All product ids regardless of price.

B. Product ids with price greater than every min_price in discounts.

C. Product ids with price equal to any min_price in discounts.

D. Product ids with price greater than at least one min_price in discounts.

Solution

1. Step 1: Understand the ALL condition

   The condition price > ALL (subquery) means price must be greater than every min_price returned.

2. Step 2: Interpret the query result

   Only products with price higher than all discount min_prices are selected.

3. Final Answer:

   Product ids with price greater than every min_price in discounts. -> Option B

4. Quick Check:

   price > ALL means greater than all values [OK]

Hint: ALL means condition holds for every subquery value [OK]

Common Mistakes:

• Confusing ALL with ANY or SOME
• Thinking it returns products with price greater than some min_price
• Assuming it returns all products

4. Identify the error in this query:

SELECT name FROM employees WHERE salary > ANY SELECT bonus FROM bonuses;

medium

A. Using ANY instead of ALL causes syntax error.

B. Incorrect use of > operator with ANY.

C. Subquery should be in FROM clause, not WHERE.

D. Missing parentheses around the subquery after ANY.

Solution

1. Step 1: Check ANY syntax

   ANY must be followed by a subquery enclosed in parentheses.

2. Step 2: Identify missing parentheses

   The query lacks parentheses around SELECT bonus FROM bonuses after ANY.

3. Final Answer:

   Missing parentheses around the subquery after ANY. -> Option D

4. Quick Check:

   ANY requires parentheses around subquery [OK]

Hint: Always put subquery in parentheses after ANY [OK]

Common Mistakes:

• Omitting parentheses around subquery
• Misplacing ANY keyword
• Confusing ANY with ALL syntax

5. You want to find all customers whose order total is less than the maximum order total of any customer in the 'orders' table. Which query correctly uses ANY to achieve this?

hard

A. SELECT customer_id FROM orders WHERE total < ANY (SELECT total FROM orders);

B. SELECT customer_id FROM orders WHERE total < ALL (SELECT total FROM orders);

C. SELECT customer_id FROM orders WHERE total > ANY (SELECT total FROM orders);

D. SELECT customer_id FROM orders WHERE total = ANY (SELECT MAX(total) FROM orders);

Solution

1. Step 1: Understand the goal

   We want customers with order total less than the maximum order total of any customer.

2. Step 2: Analyze options

   SELECT customer_id FROM orders WHERE total < ANY (SELECT total FROM orders); checks if total is less than any total in orders, which includes the maximum, so it works.

3. Step 3: Why others are wrong

   SELECT customer_id FROM orders WHERE total < ALL (SELECT total FROM orders); uses ALL, meaning less than every total, which is too strict. SELECT customer_id FROM orders WHERE total > ANY (SELECT total FROM orders); checks greater than any total, wrong direction. SELECT customer_id FROM orders WHERE total = ANY (SELECT MAX(total) FROM orders); compares to MAX(total) with ANY, which is redundant and incorrect.

4. Final Answer:

   SELECT customer_id FROM orders WHERE total < ANY (SELECT total FROM orders); -> Option A

5. Quick Check:

   Use ANY to compare with multiple values including max [OK]

Hint: Use ANY to compare with multiple values including max [OK]

Common Mistakes:

• Using ALL instead of ANY for less than max
• Comparing with MAX inside ANY incorrectly
• Confusing > and < operators