ORDER BY single column in SQL - Mini Project: Build & Apply

Sorting Products by Price Using ORDER BY

📖 Scenario: You work at a small online store. You have a table of products with their prices. You want to see the products sorted by their price from lowest to highest.

🎯 Goal: Create a SQL query that selects all products and sorts them by the price column in ascending order using ORDER BY.

📋 What You'll Learn

Create a table called products with columns id, name, and price.

Insert three products with exact values: (1, 'Pen', 1.20), (2, 'Notebook', 2.50), (3, 'Eraser', 0.80).

Write a SQL query to select all columns from products.

Use ORDER BY price to sort the results by the price column in ascending order.

💡 Why This Matters

🌍 Real World

Sorting products by price helps customers find cheaper or more expensive items easily on online stores.

💼 Career

Knowing how to use ORDER BY is essential for database querying and reporting in many jobs like data analysis, backend development, and database administration.

1

Create the products table and insert data

Create a table called products with columns id (integer), name (text), and price (decimal). Then insert these exact rows: (1, 'Pen', 1.20), (2, 'Notebook', 2.50), and (3, 'Eraser', 0.80).

SQL

-- Create table products and insert rows
-- Your code here

Hint

Use CREATE TABLE to define the table and INSERT INTO to add rows.

2

Write a basic SELECT query

Write a SQL query to select all columns from the products table using SELECT * FROM products.

SQL

CREATE TABLE products (
  id INTEGER,
  name TEXT,
  price DECIMAL
);

INSERT INTO products (id, name, price) VALUES
  (1, 'Pen', 1.20),
  (2, 'Notebook', 2.50),
  (3, 'Eraser', 0.80);

-- Write SELECT query to get all products
-- Your code here

Hint

Use SELECT * FROM products; to get all rows and columns.

3

Add ORDER BY clause to sort by price

Modify the SELECT query to add ORDER BY price so the products are sorted by the price column in ascending order.

SQL

CREATE TABLE products (
  id INTEGER,
  name TEXT,
  price DECIMAL
);

INSERT INTO products (id, name, price) VALUES
  (1, 'Pen', 1.20),
  (2, 'Notebook', 2.50),
  (3, 'Eraser', 0.80);

-- Add ORDER BY price to sort products by price
-- Your code here

Hint

Use ORDER BY price after the FROM clause to sort by price.

4

Complete the query with explicit ASC keyword

Add the keyword ASC after ORDER BY price to explicitly specify ascending order.

SQL

CREATE TABLE products (
  id INTEGER,
  name TEXT,
  price DECIMAL
);

INSERT INTO products (id, name, price) VALUES
  (1, 'Pen', 1.20),
  (2, 'Notebook', 2.50),
  (3, 'Eraser', 0.80);

-- Add ASC keyword to ORDER BY clause
-- Your code here

Hint

Use ORDER BY price ASC to sort ascending explicitly.

Practice

1. What does the SQL clause ORDER BY do when used with a single column?

easy

A. It deletes rows that have duplicate values in that column.

B. It filters the rows to only show those with unique values in that column.

C. It groups the rows by the values in that column.

D. It sorts the query results based on the values in that column.

Solution

1. Step 1: Understand the purpose of ORDER BY

   The ORDER BY clause is used to arrange the rows returned by a query in a specific order based on one or more columns.

2. Step 2: Focus on single column sorting

   When used with a single column, it sorts the results either ascending (default) or descending based on that column's values.

3. Final Answer:

   It sorts the query results based on the values in that column. -> Option D

4. Quick Check:

   ORDER BY = Sort results [OK]

Hint: ORDER BY arranges rows by column values [OK]

Common Mistakes:

• Confusing ORDER BY with filtering or grouping
• Thinking ORDER BY removes duplicates
• Assuming ORDER BY changes data in the table

2. Which of the following is the correct syntax to sort the table Employees by the column LastName in ascending order?

easy

A. SELECT * FROM Employees ORDER BY LastName DESC;

B. SELECT * FROM Employees SORT BY LastName;

C. SELECT * FROM Employees ORDER BY LastName ASC;

D. SELECT * FROM Employees ORDER LastName;

Solution

1. Step 1: Recall correct ORDER BY syntax

   The correct syntax to sort results is ORDER BY column_name. To specify ascending order, use ASC (which is also default).

2. Step 2: Check each option

   SELECT * FROM Employees ORDER BY LastName ASC; uses correct syntax with ORDER BY LastName ASC. SELECT * FROM Employees SORT BY LastName; uses invalid keyword SORT BY. SELECT * FROM Employees ORDER LastName; misses BY. SELECT * FROM Employees ORDER BY LastName DESC; sorts descending, not ascending.

3. Final Answer:

   SELECT * FROM Employees ORDER BY LastName ASC; -> Option C

4. Quick Check:

   ORDER BY + column + ASC = correct syntax [OK]

Hint: Use ORDER BY column ASC for ascending sort [OK]

Common Mistakes:

• Using SORT BY instead of ORDER BY
• Omitting BY keyword
• Confusing ASC with DESC

3. Given the table Products with columns ProductID and Price, what will be the order of ProductID after running this query?

SELECT ProductID FROM Products ORDER BY Price DESC;

Assume the data:
ProductID: 1, 2, 3
Price: 10, 30, 20

medium

A. [1, 3, 2]

B. [2, 3, 1]

C. [2, 1, 3]

D. [3, 2, 1]

Solution

1. Step 1: Understand ORDER BY Price DESC

   The query sorts rows by Price in descending order, so highest price first.

2. Step 2: Sort the data by Price descending

   Prices are 10 (ProductID 1), 30 (ProductID 2), 20 (ProductID 3). Descending order: 30, 20, 10. Corresponding ProductIDs: 2, 3, 1.

3. Final Answer:

   [2, 3, 1] -> Option B

4. Quick Check:

   Price DESC sorts highest to lowest [OK]

Hint: Sort by column DESC to get highest values first [OK]

Common Mistakes:

• Mixing ascending and descending order
• Sorting by ProductID instead of Price
• Assuming default ascending order

4. Identify the error in this SQL query:

SELECT Name FROM Customers ORDER LastName;

medium

A. Missing BY keyword after ORDER

B. ORDER BY cannot be used with SELECT

C. Name column does not exist

D. ORDER BY requires two columns

Solution

1. Step 1: Check ORDER BY syntax

   The correct syntax requires the keyword BY after ORDER. The query uses ORDER LastName which is invalid.

2. Step 2: Verify other parts

   The SELECT statement is valid, and Name is assumed to exist. ORDER BY can be used with SELECT. Only one column is needed for ORDER BY.

3. Final Answer:

   Missing BY keyword after ORDER -> Option A

4. Quick Check:

   ORDER BY requires BY keyword [OK]

Hint: ORDER BY must include BY keyword [OK]

Common Mistakes:

• Omitting BY after ORDER
• Thinking ORDER BY needs multiple columns
• Assuming ORDER BY can't be used with SELECT

5. You have a table Students with columns StudentID, Name, and Score. You want to list all students ordered by their Score from highest to lowest, but if two students have the same score, order them alphabetically by Name. Which query correctly achieves this?

hard

A. SELECT * FROM Students ORDER BY Score DESC, Name ASC;

B. SELECT * FROM Students ORDER BY Name ASC, Score DESC;

C. SELECT * FROM Students ORDER BY Score ASC, Name DESC;

D. SELECT * FROM Students ORDER BY Score DESC;

Solution

1. Step 1: Understand sorting requirements

   Primary sort is by Score descending (highest first). Secondary sort for ties is by Name ascending (alphabetical).

2. Step 2: Analyze each option

   SELECT * FROM Students ORDER BY Score DESC, Name ASC; orders by Score DESC then Name ASC, matching requirements. SELECT * FROM Students ORDER BY Name ASC, Score DESC; reverses order priorities. SELECT * FROM Students ORDER BY Score ASC, Name DESC; sorts Score ascending and Name descending, wrong directions. SELECT * FROM Students ORDER BY Score DESC; only sorts by Score DESC, no tie-breaker.

3. Final Answer:

   SELECT * FROM Students ORDER BY Score DESC, Name ASC; -> Option A

4. Quick Check:

   ORDER BY primary DESC, secondary ASC for tie-break [OK]

Hint: Use ORDER BY primary DESC, secondary ASC for tie-breaks [OK]

Common Mistakes:

• Reversing sort order directions
• Not adding secondary column for tie-break
• Using only one column when two are needed