UPPER and LOWER in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert the 'name' column to uppercase.

MySQL

SELECT [1](name) FROM employees;

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

ALOWER

BUPPER

CLENGTH

DTRIM

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOWER instead of UPPER will convert to lowercase.

Using LENGTH returns the string length, not case conversion.

The UPPER function converts all letters in a string to uppercase.

2fill in blank

medium

Complete the code to convert the 'city' column to lowercase.

MySQL

SELECT [1](city) FROM customers;

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

ALOWER

BSUBSTRING

CCONCAT

DUPPER

Attempts:

3 left

💡 Hint

Common Mistakes

Using UPPER will convert to uppercase, not lowercase.

CONCAT joins strings but does not change case.

The LOWER function converts all letters in a string to lowercase.

3fill in blank

hard

Fix the error in the code to convert 'product_name' to uppercase.

MySQL

SELECT [1](product_name) FROM products;

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

ALOWER

BUPPER)

CUPPER

DLOWER)

Attempts:

3 left

💡 Hint

Common Mistakes

Missing closing parenthesis causes syntax error.

Using LOWER instead of UPPER changes case incorrectly.

The function call must be UPPER(product_name) with parentheses around the column name.

4fill in blank

hard

Fill both blanks to convert 'last_name' to lowercase and alias it as 'lname'.

MySQL

SELECT [1](last_name) AS [2] FROM staff;

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

ALOWER

BUPPER

Clname

Dlastname

Attempts:

3 left

💡 Hint

Common Mistakes

Using UPPER instead of LOWER changes case wrongly.

Using 'lastname' as alias instead of 'lname' does not match the instruction.

Use LOWER to convert to lowercase and alias the column as lname.

5fill in blank

hard

Fill all three blanks to select 'department' in uppercase, 'manager' in lowercase, and alias 'manager' as 'mgr'.

MySQL

SELECT [1](department), [2](manager) AS [3] FROM company;

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

AUPPER

BLOWER

Cmgr

Dstaff

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up UPPER and LOWER functions.

Using wrong alias names.

Use UPPER for 'department', LOWER for 'manager', and alias 'manager' as mgr.

Practice

1. What does the MySQL function UPPER('hello') return?

easy

A. 'heLLo'

B. 'hello'

C. 'Hello'

D. 'HELLO'

Solution

1. Step 1: Understand the UPPER function

   The UPPER function converts all letters in the input text to uppercase letters.

2. Step 2: Apply UPPER to 'hello'

   Applying UPPER to 'hello' changes all letters to uppercase, resulting in 'HELLO'.

3. Final Answer:

   'HELLO' -> Option D

4. Quick Check:

   UPPER('hello') = 'HELLO' [OK]

Hint: UPPER makes all letters capital [OK]

Common Mistakes:

• Thinking UPPER only capitalizes first letter
• Confusing UPPER with LOWER
• Expecting mixed case output

2. Which of the following is the correct syntax to convert the column name to lowercase in a SELECT query?

easy

A. SELECT LOWER(name) FROM users;

B. SELECT LOWER name FROM users;

C. SELECT name.LOWER() FROM users;

D. SELECT LOWER[name] FROM users;

Solution

1. Step 1: Recall correct function syntax

   MySQL functions use the format FUNCTION_NAME(argument), so LOWER(name) is correct.

2. Step 2: Check each option

   SELECT LOWER(name) FROM users; uses correct syntax: LOWER(name). Options A, B, and D use invalid syntax forms.

3. Final Answer:

   SELECT LOWER(name) FROM users; -> Option A

4. Quick Check:

   Correct function call syntax = SELECT LOWER(name) FROM users; [OK]

Hint: Use function_name(column) syntax for MySQL functions [OK]

Common Mistakes:

• Omitting parentheses around column
• Using dot or bracket notation incorrectly
• Writing function name in lowercase without parentheses

3. Given a table products with a column category containing values 'Books', 'electronics', 'TOYS', what will the query SELECT DISTINCT UPPER(category) FROM products; return?

medium

A. ['Books', 'electronics', 'TOYS']

B. ['BOOKS', 'ELECTRONICS', 'TOYS']

C. ['books', 'electronics', 'toys']

D. ['BOOKS', 'electronics', 'TOYS']

Solution

1. Step 1: Understand UPPER and DISTINCT

   UPPER converts all text to uppercase. DISTINCT removes duplicates from the result set.

2. Step 2: Apply UPPER to each category value

   'Books' -> 'BOOKS', 'electronics' -> 'ELECTRONICS', 'TOYS' -> 'TOYS'. All become uppercase.

3. Step 3: Collect distinct uppercase values

   All three are unique after conversion, so the result is ['BOOKS', 'ELECTRONICS', 'TOYS'].

4. Final Answer:

   ['BOOKS', 'ELECTRONICS', 'TOYS'] -> Option B

5. Quick Check:

   UPPER + DISTINCT = uppercase unique values [OK]

Hint: UPPER changes all letters; DISTINCT removes duplicates [OK]

Common Mistakes:

• Expecting original case values
• Ignoring DISTINCT effect
• Mixing uppercase and lowercase in output

4. Consider the query: SELECT LOWER('MySQL') FROM dual. It returns an error. What is the likely cause?

medium

A. The table 'dual' does not exist in MySQL by default

B. LOWER function is not supported in MySQL

C. The string 'MySQL' must be in uppercase already

D. Missing semicolon at the end of the query

Solution

1. Step 1: Understand the use of 'dual'

   'dual' is a special table in Oracle but not present by default in MySQL.

2. Step 2: Check MySQL behavior

   MySQL does not require 'FROM dual' for selecting expressions; using it causes an error if 'dual' table is missing.

3. Final Answer:

   The table 'dual' does not exist in MySQL by default -> Option A

4. Quick Check:

   MySQL lacks default 'dual' table [OK]

Hint: MySQL doesn't need 'FROM dual' for expressions [OK]

Common Mistakes:

• Assuming 'dual' exists like in Oracle
• Thinking LOWER is unsupported
• Blaming missing semicolon

5. You want to find all users in the users table whose email ends with '@example.com', ignoring case differences. Which query correctly uses UPPER or LOWER to achieve this?

hard

A. SELECT * FROM users WHERE LOWER(email) LIKE '[e-mail]';

B. SELECT * FROM users WHERE LOWER(email) LIKE '[e-mail]';

C. SELECT * FROM users WHERE UPPER(email) LIKE '[e-mail]';

D. SELECT * FROM users WHERE email LIKE '[e-mail]';

Solution

1. Step 1: Understand case-insensitive matching

   To ignore case, convert both sides to the same case before comparing.

2. Step 2: Apply UPPER to email and pattern

   Using UPPER(email) and matching with uppercase pattern '[e-mail]' ensures case-insensitive match.

3. Step 3: Check options

   SELECT * FROM users WHERE UPPER(email) LIKE '[e-mail]'; correctly uses UPPER on email and uppercase pattern. SELECT * FROM users WHERE LOWER(email) LIKE '[e-mail]'; mismatches case in pattern. SELECT * FROM users WHERE email LIKE '[e-mail]'; is case-sensitive. SELECT * FROM users WHERE LOWER(email) LIKE '[e-mail]'; mismatches case in pattern.

4. Final Answer:

   SELECT * FROM users WHERE UPPER(email) LIKE '[e-mail]'; -> Option C

5. Quick Check:

   Match cases on both sides using UPPER or LOWER [OK]

Hint: Match cases on both sides with UPPER or LOWER [OK]

Common Mistakes:

• Not matching case of pattern and column
• Assuming LIKE is case-insensitive by default
• Mixing LOWER with uppercase pattern