MySQL create function for range of values with equivalent numbers

What is wrong with this function. Here is my expected output is

 1 = 10
 2 to 3 = 7
 4 to 10 = 开发者_开发知识库5
 11 to 30 = 2
 31 to 100 = 1


DELIMITER $$
DROP FUNCTION IF EXISTS `computeScore`$$
CREATE DEFINER=`root`@`localhost` FUNCTION  `computeScore`(`POS` INT(11)) RETURNS int(11)
    READS SQL DATA
    DETERMINISTIC
BEGIN
    DECLARE ordinal INT;
    SELECT (
        CASE
          WHEN POS < 2 THEN 10
          WHEN POS >= 2 < 4 THEN 7
          WHEN POS >= 4 < 11 THEN 5
          WHEN POS >= 11 < 31 THEN 2
          ELSE 1
        END )
    INTO ordinal;
    RETURN ordinal;
    RETURN 0;
END;

 $$

DELIMITER ;

Output: I always get 10

Try this:

SELECT (
        CASE
          WHEN POS < 2 THEN 10
          WHEN POS >= 2 && POS < 4 THEN 7
          WHEN POS >= 4 && POS < 11 THEN 5
          WHEN POS >= 11 && POS < 31 THEN 2
          ELSE 1
        END )

The CASE part should be

    CASE
      WHEN POS < 2 THEN 10
      WHEN POS >= 2 AND POS < 4 THEN 7
      WHEN POS >= 4 AND POS < 11 THEN 5
      WHEN POS >= 11 AND POS < 31 THEN 2
      ELSE 1
    END

What is wrong?

From the reference about SELECT..INTO statament - This SELECT syntax stores selected columns directly into variables. Therefore, only a single row may be retrieved.

Check that query returns one record.

EDIT:

The code can be like this -

SET ordinal = CASE
  WHEN pos < 2 THEN 10
  WHEN pos >= 2 AND pos < 4 THEN 7
  WHEN pos >= 4 AND pos < 11 THEN 5
  WHEN pos >= 11 AND pos < 31 THEN 2
  ELSE 1
END;