How can i sort SQL by number, length & letters? - mysql

Question

How should I sort my SELECT ?
EXAMPLE LIST
1, 2, 2A, 4, 10, 10A
SQL
$query = "SELECT * FROM table WHERE column1 = '$var' ORDER BY length(column2), column2";
If I ORDER BY length() like my example, 2A will end up in the bottom.
If I remove length(), 10 comes after 1.
How do I sort so it appears as above?

Answer 1

Like this:
$query = "SELECT * FROM table WHERE column1 = '$var' ORDER BY CAST(column2 as UNSIGNED), column2";

Answer 2

order by hex is best way to do this:
$query = "SELECT *, cast(hex(column2 as unsigned) as l FROM table WHERE column1 = '$var' ORDER BY l";

Answer 3

With a custom function such as alphas found here, you can order it by first the number portion of the value followed by the string portion of the value.
If you define and populate a table as such:
CREATE TABLE test (t VARCHAR(255));
INSERT INTO test VALUES
('10A'),
('2'),
('2A'),
('4'),
('10'),
('1');
Then create a custom function called alphas which extracts the string portion (no numbers):
DELIMITER |
DROP FUNCTION IF EXISTS alphas;
CREATE FUNCTION alphas( str CHAR(32) ) RETURNS CHAR(16)
BEGIN
DECLARE i, len SMALLINT DEFAULT 1;
DECLARE ret CHAR(32) DEFAULT '';
DECLARE c CHAR(1);
SET len = CHAR_LENGTH( str );
REPEAT
BEGIN
SET c = MID( str, i, 1 );
IF c REGEXP '[[:alpha:]]' THEN
SET ret=CONCAT(ret,c);
END IF;
SET i = i + 1;
END;
UNTIL i > len END REPEAT;
RETURN ret;
END |
DELIMITER ;
Then you can do a ordered query like this:
SELECT t FROM test ORDER BY CAST(t AS UNSIGNED), alphas(t);
The CAST function converts strings like 10A to an unsigned number of 10.