Compare and count values in mysql rows

Question

upVote   DownVote
|true   | 0
|true   | 0
|0      | true
|true   | 0
|true   | 0
|0      | true

I have columns like this above in my sql table. I want to count the total number of upVotes - Downvotes just like stackOverflow. But for some reason I am having hard time with sql syntax.

SELECT COALESCE(sum(CASE WHEN upvote THEN 1 ELSE 0 END),0) from Ratings WHERE TopicID = :topicsID

I have seen the above sql query example somewhere but not sure I am heading in the right direction.Help is appreciated

Answer 1

I guess you need to subtract on sum(upvote) and sum(DownVote)

SELECT sum(upvote) - sum(DownVote)
from Ratings 
WHERE TopicID = :topicsID

Fiddle: http://sqlfiddle.com/#!9/b1644c/8

I think One vote column with a boolean value is enough.

Because True can mean upvote ,False can mean DownVote

CREATE TABLE Ratings
(
    Vote BOOL
);
INSERT INTO Ratings VALUES 
(TRUE),
(TRUE),
(0),
(0),
(TRUE),
(TRUE),
(0);

SELECT sum(CASE WHEN Vote THEN 1 ELSE 0 END) - 
   sum(CASE WHEN Vote THEN 0 ELSE 1 END) as vote
from Ratings 
WHERE TopicID = :topicsID

Fiddle: http://sqlfiddle.com/#!9/727c2b/3

Answer 2

select COUNT(*) from ratings WHERE upvote=true AND TopicID = :topicsID ?