ALL, ANY, SOME with subqueries in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select products with a price greater than all prices in the 'discounts' table.

PostgreSQL

SELECT product_name FROM products WHERE price > [1] (SELECT discount_price FROM discounts);

Drag options to blanks, or click blank then click option'

AALL

BANY

CSOME

DIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using ANY instead of ALL returns products priced higher than any one discount price, not all.

Using IN is incorrect because it checks for equality, not comparison.

The keyword ALL compares the value to all values returned by the subquery. Here, it selects products priced higher than every discount price.

2fill in blank

medium

Complete the code to find employees whose salary is less than or equal to some salaries in the 'managers' table.

PostgreSQL

SELECT employee_name FROM employees WHERE salary <= [1] (SELECT salary FROM managers);

Drag options to blanks, or click blank then click option'

AALL

BIN

CANY

DEXISTS

Attempts:

3 left

💡 Hint

Common Mistakes

Using ALL would require the salary to be less than or equal to every manager's salary, which is stricter.

Using IN checks for equality, not comparison.

The keyword ANY means the condition is true if it matches at least one value from the subquery. Here, it finds employees earning less than or equal to at least one manager's salary.

3fill in blank

hard

Fix the error in the query to select orders with quantity greater than some quantities in 'order_details'.

PostgreSQL

SELECT order_id FROM orders WHERE quantity > [1] (SELECT quantity FROM order_details);

Drag options to blanks, or click blank then click option'

AALL

BANY

CEXISTS

DIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using ALL changes the meaning to 'greater than all', which is stricter.

Using IN checks for equality, not comparison.

The keyword ANY is correct here because we want orders with quantity greater than at least one quantity in 'order_details'. Using ALL would require quantity to be greater than every quantity, which is different.

4fill in blank

hard

Fill both blanks to select customers whose total orders are less than all totals in 'vip_orders'.

PostgreSQL

SELECT customer_id FROM customers WHERE total_orders [1] [2] (SELECT total FROM vip_orders);

Drag options to blanks, or click blank then click option'

A<

B>

CALL

DANY

Attempts:

3 left

💡 Hint

Common Mistakes

Using > ALL would select customers with totals greater than all VIP totals, which is different.

Using ANY changes the meaning to 'less than some', not all.

The operator < combined with ALL means the customer's total orders are less than every total in 'vip_orders'.

5fill in blank

hard

Fill all three blanks to select products priced greater than some prices but less than all prices in 'competitor_prices'.

PostgreSQL

SELECT product_name FROM products WHERE price [1] [2] (SELECT price FROM competitor_prices) AND price [3] (SELECT price FROM competitor_prices);

Drag options to blanks, or click blank then click option'

A>

B<

CALL

DANY

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping ALL and ANY changes the logic and results.

Using IN instead of ANY or ALL causes errors or wrong results.

The query finds products with price greater than ANY competitor price (some prices) and less than ALL competitor prices (every price). So, price > ANY and price < ALL.

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