Question

I am looking to do some basic math on my SELECT query and columns..

SELECT Rider, 
COUNT(if(Result = 1, Result, NULL)) AS "Firsts", 
COUNT(if(Result = 2, Result, NULL)) AS "Seconds", 
COUNT(if(Result = 3, Result, NULL)) AS "Thirds", 
COUNT(if(Result = " ", Result, NULL)) AS "NP",
COUNT(*) AS "Total",
"Firsts"/"Total"*100 AS "S/R"
FROM meeting_master
WHERE RaceDayDate>="2012-01-01"
GROUP BY meeting_master.Rider
ORDER BY Firsts DESC
LIMIT 100

My problem (and lack of MySQL knowledge) is to have the S/R column calculate the math in the 7th line…

Answer 1

You should not use alias in SELECT like this:

"Firsts"/"Total"*100 AS "S/R"

Instead calculate directly like this:

COUNT(if(Result = 1, Result, NULL))/COUNT(*) * 100 AS "S/R"

So your query should be:

SELECT Rider, 
COUNT(if(Result = 1, Result, NULL)) AS "Firsts", 
COUNT(if(Result = 2, Result, NULL)) AS "Seconds", 
COUNT(if(Result = 3, Result, NULL)) AS "Thirds", 
COUNT(if(Result = " ", Result, NULL)) AS "NP",
COUNT(*) AS "Total",
COUNT(if(Result = 1, Result, NULL))/COUNT(*) * 100 AS "S/R"
FROM meeting_master
WHERE RaceDayDate>="2012-01-01"
GROUP BY meeting_master.Rider
ORDER BY Firsts DESC
LIMIT 100

Just see SQLFiddle example here.