사용 별칭

Question

내 SELECT 쿼리 및 열을 몇 가지 기본적인 수학을 찾고 있어요 ..

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 

내 문제 (와 MySQL 지식의 부족)이 S/R 열 계산을하는 것입니다

7 라인에서 수학 ...

Answer 1

는이 같은 SELECT에 별칭를 사용하지 않아야합니다 :

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

대신에 다음과 같이 직접 계산 :

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

그래서 쿼리가 있어야한다 :

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.