How to Use LEFT and RIGHT Functions in MySQL

In MySQL, use the LEFT(string, number) function to get the first number characters from the start of a string, and use RIGHT(string, number) to get the last number characters from the end of a string. These functions help extract specific parts of text easily.

Syntax

The LEFT and RIGHT functions extract a substring from a string.

• LEFT(string, number): Returns the first number characters from the start of string.
• RIGHT(string, number): Returns the last number characters from the end of string.

Both functions require two arguments: the string to extract from, and how many characters to take.

sql

LEFT(str, len);
RIGHT(str, len);

Example

This example shows how to use LEFT and RIGHT to get parts of a string.

sql

SELECT
  LEFT('Hello World', 5) AS left_part,
  RIGHT('Hello World', 5) AS right_part;

Output

left_part | right_part
----------|-----------
Hello     | World

Common Pitfalls

Common mistakes include:

• Using a negative number for the length, which causes an error.
• Requesting more characters than the string length, which returns the whole string without error.
• Passing NULL as the string, which results in NULL output.

sql

/* Wrong: negative length causes error */
-- SELECT LEFT('Hello', -3);

/* Correct: use positive length */
SELECT LEFT('Hello', 3) AS correct_left;

Output

correct_left
------------
Hel

Quick Reference

Function	Description	Example	Result
LEFT(str, n)	Returns first n characters	LEFT('Apple', 3)	'App'
RIGHT(str, n)	Returns last n characters	RIGHT('Apple', 2)	'le'

Key Takeaways

Use LEFT(string, number) to get characters from the start of a string.

Use RIGHT(string, number) to get characters from the end of a string.

Length must be a positive integer; negative values cause errors.

If length is longer than the string, the whole string is returned.

Passing NULL as string returns NULL.