SUM function in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the total salary from the employees table.

SQL

SELECT [1](salary) FROM employees;

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

ASUM

BCOUNT

CAVG

DMAX

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT instead of SUM will count rows, not add values.

Using AVG will give the average, not the total.

The SUM function adds up all the values in the salary column.

2fill in blank

medium

Complete the code to find the total price of all products in the products table.

SQL

SELECT [1](price) AS total_price FROM products;

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

ASUM

BCOUNT

CMIN

DAVG

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT will count the number of products, not sum their prices.

Using AVG will calculate the average price, not the total.

The SUM function adds all the prices to get the total price.

3fill in blank

hard

Fix the error in the code to correctly calculate the total quantity from the orders table.

SQL

SELECT [1](quantity) FROM orders;

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

ACOUNT

BTOTAL

CGROUP

DSUM

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT will count rows, not sum values.

Using TOTAL is not a valid SQL function.

The correct function to add all quantities is SUM. COUNT counts rows, GROUP is not a function, and TOTAL is not standard SQL.

4fill in blank

hard

Fill both blanks to calculate the total sales for each product in the sales table.

SQL

SELECT product_id, [1](amount) AS total_amount FROM sales [2] product_id;

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

ASUM

BCOUNT

CGROUP BY

DORDER BY

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT instead of SUM will count rows, not sum amounts.

Using ORDER BY instead of GROUP BY will sort results but not group them.

Use SUM to add amounts and GROUP BY to group results by product_id.

5fill in blank

hard

Fill all three blanks to calculate the total revenue for each category in the products table.

SQL

SELECT [1], [2](price) AS total_revenue FROM products [3] category;

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

Acategory

BSUM

CGROUP BY

DORDER BY

Attempts:

3 left

💡 Hint

Common Mistakes

Using ORDER BY instead of GROUP BY will not group results.

Forgetting to select the category column will lose grouping context.

Select the category column, sum the price column, and group by category to get total revenue per category.

Practice

1. What does the SQL SUM() function do?

easy

A. Adds all numbers in a numeric column to get a total

B. Counts the number of rows in a table

C. Finds the highest value in a column

D. Deletes duplicate rows from a table

Solution

1. Step 1: Understand the purpose of SUM()

   The SUM() function is designed to add up all values in a numeric column.

2. Step 2: Compare with other functions

   Counting rows is done by COUNT(), highest value by MAX(), and deleting duplicates is unrelated.

3. Final Answer:

   Adds all numbers in a numeric column to get a total -> Option A

4. Quick Check:

   SUM() = total of numbers [OK]

Hint: SUM() always adds numbers in a column [OK]

Common Mistakes:

• Confusing SUM() with COUNT()
• Thinking SUM() works on text columns
• Assuming SUM() deletes or filters rows

2. Which of the following is the correct syntax to get the total sales from a table named Orders with a column Amount?

easy

A. SELECT COUNT(Amount) FROM Orders;

B. SELECT SUM(Amount) FROM Orders;

C. SELECT TOTAL(Amount) FROM Orders;

D. SELECT ADD(Amount) FROM Orders;

Solution

1. Step 1: Identify the correct aggregate function

   The function to add values is SUM(), so SUM(Amount) is correct.

2. Step 2: Check syntax correctness

   SUM() is standard SQL; ADD() and TOTAL() are invalid, COUNT() counts rows, not sums.

3. Final Answer:

   SELECT SUM(Amount) FROM Orders; -> Option B

4. Quick Check:

   SUM() syntax correct [OK]

Hint: SUM() is the only valid function to add column values [OK]

Common Mistakes:

• Using ADD() or TOTAL() which are not SQL functions
• Using COUNT() instead of SUM()
• Missing parentheses after SUM

3. Given the table Sales with rows:
Product | Quantity
Apple | 10
Banana | 5
Apple | 15
What is the result of the query:
SELECT SUM(Quantity) FROM Sales WHERE Product = 'Apple';

medium

A. 10

B. 15

C. 25

D. 30

Solution

1. Step 1: Filter rows where Product = 'Apple'

   Rows matching: Apple with Quantity 10 and Apple with Quantity 15.

2. Step 2: Sum the Quantity values for these rows

   10 + 15 = 25.

3. Final Answer:

   25 -> Option C

4. Quick Check:

   10 + 15 = 25 [OK]

Hint: Sum only filtered rows matching condition [OK]

Common Mistakes:

• Summing all rows ignoring WHERE clause
• Adding only one matching row
• Confusing Quantity values

4. Consider this query:
SELECT SUM(Price) FROM Products WHERE Category = 'Electronics'
It returns NULL instead of a number. What is the most likely cause?

medium

A. There are no rows with Category = 'Electronics'

B. The Price column contains text values

C. SUM() cannot be used with WHERE clause

D. The table Products does not exist

Solution

1. Step 1: Understand SUM() behavior with no matching rows

   If no rows match the WHERE condition, SUM() returns NULL.

2. Step 2: Check other options

   Price with text would cause error, SUM() works with WHERE, and table missing causes error, not NULL.

3. Final Answer:

   There are no rows with Category = 'Electronics' -> Option A

4. Quick Check:

   SUM() returns NULL if no rows match [OK]

Hint: SUM() returns NULL if no rows match WHERE [OK]

Common Mistakes:

• Assuming SUM() returns 0 when no rows match
• Thinking SUM() fails with WHERE clause
• Ignoring NULL result meaning no data

5. You have a table Orders with columns CustomerID, OrderAmount. How do you write a query to find the total order amount for each customer?

hard

A. SELECT SUM(OrderAmount) FROM Orders GROUP BY CustomerID;

B. SELECT CustomerID, SUM(OrderAmount) FROM Orders;

C. SELECT CustomerID, TOTAL(OrderAmount) FROM Orders GROUP BY CustomerID;

D. SELECT CustomerID, SUM(OrderAmount) FROM Orders GROUP BY CustomerID;

Solution

1. Step 1: Use GROUP BY to group rows by CustomerID

   This groups all orders per customer so we can sum their amounts.

2. Step 2: Use SUM(OrderAmount) to add orders per group

   SUM() calculates total order amount for each customer group.

3. Final Answer:

   SELECT CustomerID, SUM(OrderAmount) FROM Orders GROUP BY CustomerID; -> Option D

4. Quick Check:

   GROUP BY + SUM() = total per group [OK]

Hint: Use GROUP BY with SUM() to total per group [OK]

Common Mistakes:

• Missing GROUP BY causes error or wrong result
• Using TOTAL() which is not standard SQL
• Selecting SUM() without grouping CustomerID