WHERE with AND operator in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all columns from the table employees where the department is 'Sales' and the status is 'Active'.

SQL

SELECT * FROM employees WHERE department = 'Sales' [1] status = 'Active';

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

ABETWEEN

BAND

CNOT

DOR

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR instead of AND, which would select employees in Sales or Active, not both.

Using NOT which negates a condition.

Using BETWEEN which is for ranges, not combining conditions.

The AND operator is used to combine two conditions that both must be true. Here, we want employees in the Sales department who are also Active.

2fill in blank

medium

Complete the code to select name and salary from employees where the salary is greater than 50000 and the department is 'HR'.

SQL

SELECT name, salary FROM employees WHERE salary > 50000 [1] department = 'HR';

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

AAND

BOR

CLIKE

DIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR which would select employees with salary > 50000 or in HR, not necessarily both.

Using LIKE which is for pattern matching.

Using IN which checks if a value is in a list.

AND is used to ensure both conditions are true: salary greater than 50000 and department equals HR.

3fill in blank

hard

Fix the error in the query to select id from products where price is less than 100 and stock is more than 50.

SQL

SELECT id FROM products WHERE price < 100 [1] stock > 50;

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

AOR

BNOT

CAND

DXOR

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR which would select products with price < 100 or stock > 50, not both.

Using NOT which negates a condition.

Using XOR which is not standard SQL.

AND is needed to combine the two conditions so both must be true: price less than 100 and stock more than 50.

4fill in blank

hard

Fill both blanks to select username and email from users where age is greater than 18 and country is 'USA'.

SQL

SELECT username, email FROM users WHERE age [1] 18 [2] country = 'USA';

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

A>

B<

CAND

DOR

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > for age.

Using OR instead of AND which would allow either condition to be true.

The age must be greater than 18, so > is correct. The conditions are combined with AND to require both to be true.

5fill in blank

hard

Fill all three blanks to select product_name and price from products where category is 'Books', price is less than 20, and stock is more than 10.

SQL

SELECT product_name, price FROM products WHERE category = 'Books' [1] price [2] 20 [3] stock > 10;

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

AAND

B<

DOR

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR instead of AND which would select products meeting any one condition.

Using > instead of < for price comparison.

The conditions are combined with AND operators. The price comparison uses < to check less than 20.

Practice

1. What does the WHERE clause with the AND operator do in an SQL query?

easy

A. Filters rows that meet any one of the conditions

B. Joins two tables together

C. Filters rows that meet all specified conditions

D. Sorts the result set in ascending order

Solution

1. Step 1: Understand the WHERE clause

   The WHERE clause filters rows based on conditions given in the query.

2. Step 2: Understand the AND operator

   The AND operator requires all conditions to be true for a row to be included.

3. Final Answer:

   Filters rows that meet all specified conditions -> Option C

4. Quick Check:

   WHERE + AND = all conditions true [OK]

Hint: AND means all conditions must be true together [OK]

Common Mistakes:

• Thinking AND means any condition can be true
• Confusing WHERE with JOIN
• Assuming AND sorts data

2. Which of the following is the correct syntax to select rows where age is greater than 18 AND city is 'New York'?

easy

A. SELECT * FROM users WHERE age > 18 AND city = 'New York';

B. SELECT * FROM users WHERE age > 18, city = 'New York';

C. SELECT * FROM users WHERE age > 18 OR city = 'New York';

D. SELECT * FROM users WHERE age > 18 AND city == 'New York';

Solution

1. Step 1: Check the operator between conditions

   The question asks for AND, so the operator must be AND, not OR or comma.

2. Step 2: Check the comparison operators

   Use single equals (=) for comparison in SQL, not double equals (==).

3. Final Answer:

   SELECT * FROM users WHERE age > 18 AND city = 'New York'; -> Option A

4. Quick Check:

   AND + = correct syntax [OK]

Hint: Use AND and single = for conditions in WHERE [OK]

Common Mistakes:

• Using OR instead of AND
• Using comma instead of AND
• Using == instead of = for comparison

3. Given the table employees with columns name, department, and salary, what will this query return?

SELECT name FROM employees WHERE department = 'Sales' AND salary > 50000;

medium

A. Names of employees in Sales with salary over 50000

B. Names of employees in Sales or salary over 50000

C. All employees with salary over 50000

D. Syntax error due to missing OR

Solution

1. Step 1: Analyze the WHERE clause conditions

   The query filters rows where department equals 'Sales' AND salary is greater than 50000.

2. Step 2: Understand the AND effect

   Only employees meeting both conditions will be selected, so names returned are from Sales with salary above 50000.

3. Final Answer:

   Names of employees in Sales with salary over 50000 -> Option A

4. Quick Check:

   AND filters both conditions true [OK]

Hint: AND means both conditions must be true to select rows [OK]

Common Mistakes:

• Thinking OR is used instead of AND
• Assuming it returns all employees with salary > 50000
• Believing syntax error occurs without OR

4. Identify the error in this SQL query:

SELECT * FROM products WHERE price > 100 AND category 'Electronics';

medium

A. AND should be OR

B. Missing comparison operator (=) before 'Electronics'

C. price > 100 is invalid syntax

D. Missing FROM keyword

Solution

1. Step 1: Check the WHERE clause syntax

   The condition after AND is missing a comparison operator before 'Electronics'. It should be category = 'Electronics'.

2. Step 2: Verify other parts

   price > 100 is correct, AND is valid, and FROM is present.

3. Final Answer:

   Missing comparison operator (=) before 'Electronics' -> Option B

4. Quick Check:

   Comparison operator needed before value [OK]

Hint: Each condition needs a comparison operator like = [OK]

Common Mistakes:

• Omitting = in conditions
• Replacing AND with OR incorrectly
• Ignoring syntax errors in WHERE clause

5. You have a table orders with columns order_id, customer_id, status, and total. Write a query to find all orders with status 'shipped' AND total greater than 100, but exclude orders where customer_id is NULL. Which query is correct?

hard

A. SELECT * FROM orders WHERE status = 'shipped' AND total > 100 AND customer_id != NULL;

B. SELECT * FROM orders WHERE status = 'shipped' OR total > 100 AND customer_id IS NOT NULL;

C. SELECT * FROM orders WHERE status = 'shipped' AND total > 100 OR customer_id IS NOT NULL;

D. SELECT * FROM orders WHERE status = 'shipped' AND total > 100 AND customer_id IS NOT NULL;

Solution

1. Step 1: Combine conditions with AND

   We want orders where status is 'shipped' AND total is greater than 100 AND customer_id is not NULL.

2. Step 2: Use correct syntax for NULL check

   In SQL, to check for NULL, use IS NOT NULL, not != NULL.

3. Final Answer:

   SELECT * FROM orders WHERE status = 'shipped' AND total > 100 AND customer_id IS NOT NULL; -> Option D

4. Quick Check:

   Use AND and IS NOT NULL for correct filtering [OK]

Hint: Use IS NOT NULL to exclude NULLs with AND [OK]

Common Mistakes:

• Using OR instead of AND
• Using != NULL instead of IS NOT NULL
• Mixing AND and OR without parentheses