ISSUE: Mysql converting Enum to Int

Question

I have a very simple rating system in my database where each rating is stored as an enum(\'1\',\'-1\'). To calculate the total I tried using this statement:

Answer 1

I wouldn't use enum here too, but it is still possible in this case to get what is needed

Creating table:

CREATE TABLE test (
    _id INT PRIMARY KEY,
    rating ENUM('1', '-1')
);

Filling table:

INSERT INTO test VALUES(1, "1"), (2, "1"), (3, "-1"), (4, "-1"), (5, "-1");

Performing math operations on enums converts them to indexes, so it is possible just to scale the result value:

SELECT 
    SUM(3 - rating * 2)
FROM
    test;

Result: -1 which is true for the test case.

Answer 2

this is what you want

select enum+0 as enum

Answer 3

use

SELECT SUM( IF( columnname >0, CAST( columnname AS CHAR ) , NULL ) ) AS vals
FROM `tableName` 

Answer 4

Yes, I'd suggest to change the type of the column. The issue becomes clear when you read the doc about enum type (which strongly recommends not to use numbers as enumeration values!) - the index of the enum item is returned, not the enum value itself.

Answer 5

Ok guys,

Just had a bit of a mere of a time with this one. I learned that i shouldn't use ENUMs where integers are the values. However We had years worth of data and i couldn't alter the database.

This bad boy worked (turning it into a character, then into a signed int).

CAST(CAST(`rating` AS CHAR) AS SIGNED) as value from table WHERE _id = 1

Answer 6

This conversion to int in MySQL for enum is only possible:

CAST(CAST(`rating` AS CHAR) AS SIGNED) as value from table WHERE _id = 1