select length('€'), char_length('€') --> 1, 1
LENGTH() returns the length of the string measured in bytes.CHAR_LENGTH() returns the length of the string measured in characters.
This is especially relevant for Unicode, in which most characters are encoded in two bytes. Or UTF-8, where the number of bytes varies. For example:
select length(_utf8 '€'), char_length(_utf8 '€') --> 3, 1
CHAR_LENGTH() gives precise result than LENGTH() function.