What's the main difference between length() and char_length()?
I believe it has something to do with binary and non-binary strings. Is there any practical reason to store strings as binary?
mysql> select length('MySQL'), char_length('MySQL');
+-----------------+----------------------+
| length('MySQL') | char_length('MySQL') |
+-----------------+----------------------+
| 5 | 5 |
+-----------------+----------------------+
1 row in set (0.01 sec)
Answer
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
As you can see the Euro sign occupies 3 bytes (it's encoded as 0xE282AC in UTF-8) even though it's only one character.