DISTINCT for unique values in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select unique city names from the customers table.

SQL

SELECT [1] city FROM customers;

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ADISTINCT

BUNIQUE

CALL

DSINGLE

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE instead of DISTINCT, which is not standard SQL.

Omitting DISTINCT and getting duplicate city names.

The DISTINCT keyword returns only unique values in the result set.

2fill in blank

medium

Complete the code to count how many unique product names are in the products table.

SQL

SELECT COUNT([1]) FROM products;

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AALL product_name

BDISTINCT product_name

Cproduct_name

DUNIQUE product_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT(product_name) which counts all rows, not unique ones.

Using UNIQUE inside COUNT, which is not valid SQL.

Using COUNT(DISTINCT column) counts only unique values in that column.

3fill in blank

hard

Fix the error in the query to select unique customer IDs from orders.

SQL

SELECT [1] customer_id FROM orders;

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AUNIQUE

BSINGLE

CONLY

DDISTINCT

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE which causes syntax error.

Using ONLY or SINGLE which are not valid SQL keywords here.

DISTINCT is the correct SQL keyword to get unique values. UNIQUE is not valid here.

4fill in blank

hard

Complete the code to select unique combinations of first and last names from employees.

SQL

SELECT [1] first_name, last_name FROM employees;

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AUNIQUE

BALL

CDISTINCT

DSINGLE

Attempts:

3 left

💡 Hint

Common Mistakes

Putting DISTINCT before both columns, which causes syntax error.

Using UNIQUE instead of DISTINCT.

DISTINCT is placed after SELECT and applies to all listed columns, returning only unique combinations of first_name and last_name.

5fill in blank

hard

Fill all three blanks to select unique department names and count employees in each department.

SQL

SELECT [1] department_name, COUNT([2]) FROM employees GROUP BY [3];

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ADISTINCT

B*

Cdepartment_name

DALL

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting DISTINCT and getting duplicate department names.

Using COUNT(department_name) instead of COUNT(*).

Not grouping by department_name.

Use DISTINCT to get unique department names. COUNT(*) counts all employees per group. GROUP BY department_name groups rows by department.