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length

Use the length() function to find the length of a string (for example, the number of characters in a given string). It accepts a string as a parameter. The syntax of the length function is:

LENGTH(string)

The input type is a string, and the return type is int, as it returns the number of characters.

Special cases:

  • If a NULL value is passed in the function. (For example, LENGTH(NULL), it returns NULL).

  • If the parameter is an empty string LENGTH(''), it returns 0.

  • If the parameter is a space character LENGTH(' '), not empty or NULL, it returns 1 as it is not empty anymore.

Examples

Basic length() function

This example uses the length() function to find out the length of a string text:

SELECT LENGTH ('Redpanda SQL Tutorial');

The query returns:

+------------+
| length     |
+------------+
| 21         |
+------------+

length() function using columns

The following example uses the length() function on a personal_details table containing id, first_name, last_name, and gender columns for retail store employees.

CREATE TABLE personal_details (
  id int,
  first_name text,
  last_name text,
  gender text
);
INSERT INTO personal_details
    (id, first_name, last_name, gender)
VALUES
    (1,'Mark','Wheeler','M'),
    (2,'Tom','Hanks','M'),
    (3,'Jane','Hopper','F'),
    (4,'Emily','Byers','F'),
    (5,'Lucas','Sinclair','M');
SELECT * FROM personal_details;

The query shows this table:

+-----+-------------+-------------+----------+
| id  | first_name  | last_name   | gender   |
+-----+-------------+-------------+----------+
| 1   | Mark        | Wheeler     | M        |
| 2   | Tom         | Hanks       | M        |
| 3   | Jane        | Hopper      | F        |
| 4   | Emily       | Byers       | F        |
| 5   | Lucas       | Sinclair    | M        |
+-----+-------------+-------------+----------+

The query returns the last name and the length of the last name from the personal_details table, where the length of the last_name is greater than 5.

SELECT last_name,length(last_name)
AS "Length of Last Name"
FROM personal_details
WHERE LENGTH(last_name) > 5;

The output displays all those items in the last_name column with a length of more than 5 characters:

+---------------+-----------------------+
| last_name     | Length of Last Name   |
+---------------+-----------------------+
| Wheeler       | 7                     |
| Hopper        | 6                     |
| Sinclair      | 8                     |
+---------------+-----------------------+