TRIM, LTRIM, RTRIM in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the TRIM function do in MySQL?

TRIM removes spaces or specified characters from both the beginning and the end of a string.

beginner

How does LTRIM differ from TRIM?

LTRIM removes spaces only from the left (start) side of a string.

beginner

What is the purpose of RTRIM in MySQL?

RTRIM removes spaces only from the right (end) side of a string.

beginner

Write a MySQL query to remove spaces from both ends of the string ' hello '.

SELECT TRIM(' hello ') AS trimmed_string; -- Result: 'hello'

intermediate

Can TRIM remove characters other than spaces? How?

Yes, TRIM can remove other characters by specifying them. For example, TRIM(BOTH 'x' FROM 'xxhelloxx') removes 'x' from both ends.

Which function removes spaces only from the start of a string in MySQL?

A LTRIM

B RTRIM

C TRIM

D SUBSTR

LTRIM removes spaces from the left (start) side of the string.

What will SELECT TRIM(' data ') return?

A 'data '

B ' data'

C ' data '

D 'data'

TRIM removes spaces from both ends, so the result is 'data'.

Which function removes spaces only from the right side of a string?

A RTRIM

B LTRIM

C TRIM

D LEFT

RTRIM removes spaces from the right (end) side of the string.

How do you remove the character 'x' from both ends of 'xxhelloxx' in MySQL?

A TRIM('xxhelloxx')

B LTRIM('xxhelloxx')

C TRIM(BOTH 'x' FROM 'xxhelloxx')

D RTRIM('xxhelloxx')

TRIM with BOTH and character specified removes that character from both ends.

If you want to remove spaces only from the right side of a string, which function should you use?

A LTRIM

B RTRIM

C TRIM

D REPLACE

RTRIM removes spaces from the right side only.

Explain the difference between TRIM, LTRIM, and RTRIM functions in MySQL.

Think about which side of the string each function affects.

How can you use TRIM to remove a specific character other than space from a string?

TRIM is flexible and can remove characters you specify.

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