MySQL Order By doesn't work on Concat(enum) - mysql

Question

Currently we have an interessting problem regarding the sort order of MySQL in an enum-field. The fields enum entries have been sorted in the order we want it. Just to be save, we added a CONCAT around it, so it would be cast to char and ordered in alphabetical order, just as suggested by the MySQL-reference (MySQL Reference - Enum)
Make sure that the column is sorted lexically rather than by index number by coding ORDER BY CAST(col AS CHAR) or ORDER BY CONCAT(col).
But that didn't produce the expected results, so we started to investigate further. It seems that the order by statement doesn't work on a combination of enum and the concat function. I've wrote the following sample script, which should show my point:
CREATE TABLE test (
`col1` enum('a','b','c') COLLATE utf8_bin DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
INSERT INTO test
VALUES ('b'), ('c'), ('a');
SELECT * FROM test; -- b, c, a
SELECT * FROM test ORDER BY col1 ASC; -- a, b, c
SELECT * FROM test ORDER BY CAST(col1 AS CHAR) ASC; -- a, b, c
SELECT * FROM test ORDER BY CAST(col1 AS BINARY) ASC; -- a, b, c
SELECT * FROM test ORDER BY CONCAT(col1) ASC; -- b, c, a - This goes wrong
I am currently suspecting some kind of problem with the collation/encoding, but I'm not sure. My databases default encoding is also utf8. The MySQL version is 5.6.12 but it seems to be reproduceable with MySQL 5.1. The storage engine is MyIsam but it also occurs with the memory engine.
Any help would be appreciated.
Update:
As it seems the problem is produced only in MySQL 5.6 and by the collation of the column. With the first CREATE TABLE statement, the queries work fine.
CREATE TABLE test (
`col1` enum('a','b','c') COLLATE utf8_general_ci DEFAULT NULL
)
With the second they don't.
CREATE TABLE test (
`col1` enum('a','b','c') COLLATE utf8_bin DEFAULT NULL
)
The collation of the table and/or database don't seem to affect the queries. The queries can be tested in this SQL Fiddle

Answer 1

Strange,it works in this fiddle.Do you have a trigger or something?
http://sqlfiddle.com/#!2/0976a/2
BUT,in 5.6 goes haywire:
http://sqlfiddle.com/#!9/0976a/1
Mysql bug,probably.
More,if you input the values in the enum in the "proper" order it works:
http://sqlfiddle.com/#!9/a3784/1
IN the doc:
ENUM values are sorted based on their index numbers, which depend on
the order in which the enumeration members were listed in the column
specification. For example, 'b' sorts before 'a' for ENUM('b', 'a').

Answer 2

As per the document:
Under the Handling of Enumeration Literals section, it states that:
If you store a number into an ENUM column, the number is treated as
the index into the possible values, and the value stored is the
enumeration member with that index. (However, this does not work with
LOAD DATA, which treats all input as strings.) If the numeric value is
quoted, it is still interpreted as an index if there is no matching
string in the list of enumeration values. For these reasons, it is not
advisable to define an ENUM column with enumeration values that look
like numbers, because this can easily become confusing.
For example, the following column has enumeration members with string values of '0', '1', and '2', but numeric index values of 1, 2, and 3:
numbers ENUM('0','1','2')
If you store 2, it is interpreted as an
index value, and becomes '1' (the value with index 2). If you store
'2', it matches an enumeration value, so it is stored as '2'. If you
store '3', it does not match any enumeration value, so it is treated
as an index and becomes '2' (the value with index 3).
mysql> INSERT INTO t (numbers) VALUES(2),('2'),('3');
mysql> SELECT * FROM t;
+---------+
| numbers |
+---------+
| 1 |
| 2 |
| 2 |
+---------+
In your case:
INSERT INTO test
VALUES ('2'), ('3'), ('1');
Index value of '2' is 2, '3' is 3 and '1' is 1.
So the output is 2,3,1