20 SQL Practice Problems for Beginners with Solutions

Solution

SELECT item_name, price_usd
FROM menu_items;

Explanation

SELECT tells the database which columns to return. By listing item_name and price_usd, only those two columns appear in the results — all other columns like category and calories are left out. FROM tells the database which table to pull from.

Solution

SELECT *
FROM menu_items;

Explanation

The asterisk (*) is a shorthand that means "give me every column." This is useful when you're exploring a table for the first time and want to see all the data. Every row and every column in the table will be returned.

Solution

SELECT first_name, last_name, email
FROM customers;

Explanation

Listing three column names after SELECT tells the database to return only those three columns for every row. The customer_id, signup_date, and city columns are excluded from the results because they weren't listed.

Solution

SELECT *
FROM menu_items
WHERE category = 'Dessert';

Explanation

WHERE category = 'Dessert' tells the database to only return rows where the category column equals 'Dessert'. Every other row is filtered out. Notice the text value is wrapped in single quotes — this is required for text comparisons in SQL.

Solution

SELECT *
FROM customers
WHERE city = 'New York';

Explanation

WHERE city = 'New York' filters the results so only customers from New York are returned. All customers from other cities are excluded. SELECT * means all columns are shown for the matching rows.

Solution

SELECT *
FROM products
WHERE price_usd > 50;

Explanation

WHERE price_usd > 50 filters to only rows where the price is greater than 50. Notice there are no quotes around the number — in SQL, quotes are only used for text values, never for numbers. Every product priced at $50 or less is excluded.

Solution

SELECT product_name, price_usd
FROM products
ORDER BY price_usd;

Explanation

ORDER BY price_usd sorts the results by price. When you don't specify ASC or DESC, SQL defaults to ascending order — meaning the lowest price appears first. This is the correct behavior for "cheapest to most expensive."

Solution

SELECT first_name, signup_date
FROM customers
ORDER BY signup_date DESC;

Explanation

ORDER BY signup_date DESC sorts dates in descending order — most recent first, oldest last. Without DESC, the oldest signup date would appear first. Always add DESC when you want newest, largest, or highest values at the top.

Solution

SELECT item_name, category
FROM menu_items
ORDER BY item_name;

Explanation

ORDER BY item_name sorts text columns alphabetically from A to Z by default. This makes it easy to scan through menu items in alphabetical order. If you wanted Z to A, you'd add DESC.

Solution

SELECT *
FROM products
LIMIT 5;

Explanation

LIMIT 5 tells the database to stop returning rows after the first 5. This is useful when you just want a quick look at what a table contains without retrieving thousands of rows. SELECT * returns all columns for those 5 rows.

Solution

SELECT item_name, price_usd
FROM menu_items
ORDER BY price_usd DESC
LIMIT 3;

Explanation

ORDER BY price_usd DESC sorts all items from most to least expensive first. Then LIMIT 3 keeps only the top 3 rows from that sorted result. This ORDER BY + LIMIT combination is the standard pattern for finding the top N results in SQL.

Solution

SELECT first_name, signup_date
FROM customers
ORDER BY signup_date DESC
LIMIT 10;

Explanation

ORDER BY signup_date DESC puts the most recent signups at the top. LIMIT 10 then keeps only the first 10 rows from that sorted list — giving you the 10 most recently signed up customers.

Solution

SELECT COUNT(*) AS total_customers
FROM customers;

Explanation

COUNT(*) counts every row in the table regardless of what values the columns contain. AS total_customers gives the result a readable column name instead of just showing "COUNT(*)". The result is a single number — the total number of rows in the customers table.

Solution

SELECT COUNT(*) AS electronics_count
FROM products
WHERE category = 'Electronics';

Explanation

WHERE category = 'Electronics' filters the rows first, keeping only Electronics products. COUNT(*) then counts how many rows remain after that filter. Combining WHERE with COUNT is how you count rows that meet a specific condition.

Solution

SELECT COUNT(*) AS affordable_items
FROM menu_items
WHERE price_usd < 10;

Explanation

WHERE price_usd < 10 filters to only rows where the price is below $10. COUNT(*) counts how many rows match that condition. The result is a single number telling you how many menu items are priced under $10.

Solution

SELECT item_name, price_usd
FROM menu_items
WHERE calories < 500;

Explanation

SELECT chooses which columns to display — just item_name and price_usd. WHERE calories < 500 filters the rows so only low-calorie items appear. The calories column itself doesn't need to be in your SELECT list to use it as a filter condition.

Solution

SELECT *
FROM products
WHERE category = 'Clothing'
ORDER BY price_usd DESC;

Explanation

WHERE category = 'Clothing' filters to only Clothing products. ORDER BY price_usd DESC then sorts those filtered results from most to least expensive. The clause order matters — WHERE always comes before ORDER BY.

Solution

SELECT item_name, calories
FROM menu_items
ORDER BY calories
LIMIT 5;

Explanation

ORDER BY calories sorts all items from lowest to highest calorie count. LIMIT 5 then keeps only the first 5 rows from that sorted list — giving the 5 lowest-calorie items. No DESC is needed here because we want the lowest values first, which is the default ascending order.

Solution

SELECT COUNT(*) AS chicago_customers
FROM customers
WHERE city = 'Chicago';

Explanation

WHERE city = 'Chicago' filters to only Chicago customers. COUNT(*) then counts how many rows match. The result is a single number — the total count of customers from Chicago. AS chicago_customers gives the result column a clear, readable name.

Solution

SELECT product_name, price_usd
FROM products
WHERE category = 'Electronics'
ORDER BY price_usd DESC
LIMIT 3;

Explanation

This query uses three clauses together. WHERE category = 'Electronics' filters to only Electronics products. ORDER BY price_usd DESC sorts those products from most to least expensive. LIMIT 3 keeps only the top 3 from that sorted list. This is a great example of how SQL clauses build on each other — filter first, sort second, limit third.