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:
SELECT SUM(CONVERT(rating, SIGNED)) as value from table WHERE _id = 1
This works fine for the positive 1 but for some reason the -1 are parsed out to 2's.
Can anyone help or offer incite?
Or should I give up and just change the column to a SIGNED INT(1)?
this is what you want
select enum+0 as enum
rating AS CHAR) AS SIGNED) is the right solutionThis conversion to int in MySQL for enum is only possible:
CAST(CAST(`rating` AS CHAR) AS SIGNED) as value from table WHERE _id = 1
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.
up and down!
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
use
SELECT SUM( IF( columnname >0, CAST( columnname AS CHAR ) , NULL ) ) AS vals
FROM `tableName`
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.
