Syntax:
LENGTH(str)

Returns the length of the string str, measured in bytes. A multibyte
character counts as multiple bytes. This means that for a string
containing five 2-byte characters, LENGTH() returns 10, whereas
CHAR_LENGTH() returns 5. Returns NULL if str is NULL.

URL: https://dev.mysql.com/doc/refman/8.0/en/string-functions.html

