CHARLENGTH

CHARLENGTH is a function used in SQL and related database systems to determine the number of characters in a string. In the SQL standard, the function is called CHARACTER_LENGTH, and CHAR_LENGTH is commonly provided as an alias. The result represents the count of user-perceived characters, not the underlying storage size in bytes.

Behavior and compatibility vary by database. In many systems, CHAR_LENGTH and CHARACTER_LENGTH are interchangeable and return the number of characters in the input. Some databases distinguish between character length and byte length; for example, a string in a multibyte character set may occupy more than one byte per character. In such cases, a separate function often exists to report the byte length. Because of this, CHAR_LENGTH is most reliable when the database adheres to the standard aliasing between character length functions.

NULL handling also follows common SQL rules: if the input is NULL, the result is NULL. The exact behavior can vary if the database applies specific null semantics, but the typical outcome is a NULL result.

Unicode and multibyte considerations are important. When strings use multibyte encodings (such as UTF-8), CHAR_LENGTH counts characters, not bytes, which can differ from a byte-length function.

Examples:

- SELECT CHAR_LENGTH('Hello') returns 5.

- SELECT CHAR_LENGTH('こんにちは') returns 5 in systems that count by characters (not bytes).

See also: LENGTH, OCTET_LENGTH, CHARACTER_LENGTH, char_length, byte length functions.