In MySQL, the LENGTH function is used to determine the length of a string. The length is defined as the number of characters in a string, including spaces and special characters. The syntax for the LENGTH function is quite straightforward:

Syntax

LENGTH(str)

Here, str is the string whose length you want to calculate. It can be a column name, a string literal, or an expression that evaluates to a string.

Example

Let’s look at a few examples to better understand how the LENGTH function works:

Using with a String Literal

SELECT LENGTH('Hello, World!') AS StringLength;

Output:

+--------------+
| StringLength |
+--------------+
| 13           |
+--------------+

In this example, the length of the string ‘Hello, World!’ is 13 characters.

Using with a Column

Consider a table named employees with a column first_name:

SELECT first_name, LENGTH(first_name) AS NameLength FROM employees;

Output:

+------------+------------+
| first_name | NameLength |
+------------+------------+
| John       | 4          |
| Mary       | 4          |
| Robert     | 6          |
+------------+------------+

This query retrieves the first_name column from the employees table along with the length of each name.

Using with an Expression

SELECT 
CONCAT('First', 'Second') AS Concatenated, 
LENGTH(CONCAT('First', 'Second')) AS TotalLength;

Output:

+--------------+-------------+
| Concatenated | TotalLength |
+--------------+-------------+
| FirstSecond  | 11          |
+--------------+-------------+

Here, the CONCAT function is used to concatenate the strings ‘First’ and ‘Second’, and then the LENGTH function calculates the length of the resulting string.

It’s essential to note that the LENGTH function in MySQL returns the number of characters, not the number of bytes. If you need the length in bytes, you can use the CHAR_LENGTH function or the OCTET_LENGTH function. Additionally, for character sets like UTF-8, where characters can be represented by multiple bytes, the length might not be the same as the number of characters.