TRIM, LTRIM, RTRIM in MySQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Output of TRIM function on padded string

What is the output of the following MySQL query?

SELECT TRIM('  Hello World  ') AS trimmed_text;

MySQL

SELECT TRIM('  Hello World  ') AS trimmed_text;

A ' Hello World '

B 'Hello World'

C 'Hello World '

D ' Hello World'

💡 Hint

TRIM removes spaces from both sides of the string.

The TRIM function removes leading and trailing spaces from the string, so the output is 'Hello World' without spaces on either side.

❓ query_result

intermediate

Output of LTRIM on string with leading spaces

What will this MySQL query return?

SELECT LTRIM('   DataBase') AS left_trimmed;

MySQL

SELECT LTRIM('   DataBase') AS left_trimmed;

A 'DataBase'

B 'DataBase '

C ' DataBase'

D 'Data Base'

💡 Hint

LTRIM removes spaces only from the left side.

LTRIM removes only the spaces on the left side of the string, so the output is 'DataBase' without leading spaces.

📝 Syntax

advanced

Identify the syntax error in RTRIM usage

Which option contains a syntax error when using RTRIM in MySQL?

A SELECT RTRIM('Test String ') AS trimmed;

B SELECT RTRIM('Test String ') trimmed;

C SELECT RTRIM('Test String ') AS trimmed_string;

D SELECT RTRIM 'Test String ' AS trimmed;

💡 Hint

Check the function call syntax with parentheses.

RTRIM requires parentheses around the string argument. Option D misses parentheses, causing a syntax error.

❓ query_result

advanced

Result of nested TRIM functions

What is the output of this query?

SELECT TRIM(TRAILING 'x' FROM LTRIM('xxxHello Worldxxx')) AS result;

MySQL

SELECT TRIM(TRAILING 'x' FROM LTRIM('xxxHello Worldxxx')) AS result;

A 'xxxHello World'

B 'Hello Worldxxx'

C 'xxHello World'

D 'Hello World'

💡 Hint

LTRIM removes spaces, not 'x'. TRIM with TRAILING removes 'x' only from the right side.

LTRIM does not remove 'x' characters, so the string remains 'xxxHello Worldxxx'. TRIM(TRAILING 'x' FROM ...) removes 'x' only from the right end, leaving 'xxxHello World'.

🧠 Conceptual

expert

Understanding difference between TRIM, LTRIM, and RTRIM

Given the string ' SQL Query ', which function(s) will remove spaces only from the right side?
Choose the correct statement.

A TRIM removes spaces only from the right side.

B LTRIM removes spaces only from the right side.

C RTRIM removes spaces only from the right side.

D LTRIM and RTRIM both remove spaces only from the right side.

💡 Hint

Think about what each function does: left, right, or both sides.

RTRIM removes spaces only from the right side of the string. LTRIM removes from the left, and TRIM removes from both sides.

Practice

1. What does the TRIM function do in MySQL?

easy

A. Removes spaces or specified characters from both ends of a string

B. Removes spaces only from the start of a string

C. Removes spaces only from the end of a string

D. Replaces spaces inside the string with underscores

Solution

1. Step 1: Understand the purpose of TRIM

   The TRIM function is designed to remove unwanted spaces or characters from the start and end of a string.

2. Step 2: Compare with LTRIM and RTRIM

   LTRIM removes only from the left, RTRIM only from the right, but TRIM does both ends.

3. Final Answer:

   Removes spaces or specified characters from both ends of a string -> Option A

4. Quick Check:

   TRIM = both ends removal [OK]

Hint: TRIM cleans both sides of spaces or chars [OK]

Common Mistakes:

• Confusing TRIM with LTRIM or RTRIM
• Thinking TRIM removes spaces inside the string
• Assuming TRIM only removes spaces from one side

2. Which of the following is the correct syntax to remove spaces from the left side of a string ' hello' in MySQL?

easy

A. RTRIM(' hello')

B. LTRIM(' hello')

C. TRIM(' hello')

D. REMOVE_LEFT(' hello')

Solution

1. Step 1: Identify the function for left-side trimming

   LTRIM is the MySQL function that removes spaces from the start (left side) of a string.

2. Step 2: Check other options

   RTRIM removes spaces from the right side, TRIM removes from both ends, and REMOVE_LEFT is not a valid MySQL function.

3. Final Answer:

   LTRIM(' hello') -> Option B

4. Quick Check:

   LTRIM = left side spaces removed [OK]

Hint: Use LTRIM() to remove left spaces [OK]

Common Mistakes:

• Using RTRIM instead of LTRIM
• Using TRIM when only left spaces needed
• Using non-existent functions like REMOVE_LEFT

3. What is the output of this query?
SELECT CONCAT('[', TRIM(' abc '), ']') AS result;

medium

A. [abc]

B. [ abc ]

C. [abc ]

D. [ abc]

Solution

1. Step 1: Understand TRIM effect on the string

   TRIM removes spaces from both the start and end of ' abc ', resulting in 'abc'.

2. Step 2: Apply CONCAT with brackets

   Concatenating '[' + 'abc' + ']' results in '[abc]'.

3. Final Answer:

   [abc] -> Option A

4. Quick Check:

   TRIM removes spaces both ends = '[abc]' [OK]

Hint: TRIM removes spaces both ends, so output is '[abc]' [OK]

Common Mistakes:

• Thinking TRIM removes spaces only from one side
• Ignoring spaces inside the string
• Confusing CONCAT output formatting

4. Identify the error in this query:
SELECT LTRIM(' test') FROM dual WHERE RTRIM('test ') = 'test';

medium

A. No error, query runs correctly

B. RTRIM cannot be used in WHERE clause

C. LTRIM and RTRIM functions are misspelled

D. Using FROM dual is invalid in MySQL

Solution

1. Step 1: Check the use of FROM dual in MySQL

   MySQL does not require or support the FROM dual syntax; it is used in Oracle.

2. Step 2: Verify function usage and WHERE clause

   LTRIM and RTRIM are valid functions and can be used in WHERE clauses in MySQL.

3. Final Answer:

   Using FROM dual is invalid in MySQL -> Option D

4. Quick Check:

   FROM dual is Oracle-specific, not MySQL [OK]

Hint: MySQL does not use FROM dual [OK]

Common Mistakes:

• Assuming FROM dual works in MySQL
• Thinking RTRIM can't be in WHERE clause
• Misspelling function names

5. You have a table users with a column username that may have extra spaces at the start or end. Which query correctly updates the table to remove all leading and trailing spaces from username?

hard

A. UPDATE users SET username = LTRIM(username);

B. UPDATE users SET username = RTRIM(username);

C. UPDATE users SET username = TRIM(username);

D. UPDATE users SET username = REPLACE(username, ' ', '');

Solution

1. Step 1: Understand how to remove spaces from both ends

   TRIM removes spaces from both the start and end of a string in one call.

2. Step 2: Check LTRIM and RTRIM options

   LTRIM removes only leading spaces, RTRIM only trailing spaces. Neither handles both ends alone.

3. Step 3: Check REPLACE option

   REPLACE removes all spaces inside the string, not just at ends, which is incorrect here.

4. Final Answer:

   UPDATE users SET username = TRIM(username); -> Option C

5. Quick Check:

   TRIM cleans both ends simply [OK]

Hint: Use TRIM() to clean both ends in one step [OK]

Common Mistakes:

• Using LTRIM which only removes leading spaces
• Using RTRIM which only removes trailing spaces
• Using REPLACE which removes all spaces