MySQL 중첩 SELECT

Question

나는이 쿼리로 머리를 쓰고있다.

Date   Weight kg 
------------------- 
2012-04-16  12.4 
2012-04-17  9.6 
2012-04-16  5.4 
2012-04-18  2.8 
2012-04-16  4.5 
...    ... 

내가 쿼리는이 결과를 반환 할 : :이 같은 (간체)을 보이는 테이블이

Week.no. <3kg 3-7kg >7kg 
---------------------------- 
16   2.8 9.9 22.0 
...  ... ... .... 

이것은 내가 지금까지 무엇을 가지고 :

SELECT *, CONCAT(WEEK(`Date`)) AS Week, SUM(`Weight`) AS TotalWeight, 
    (SELECT SUM(`Weight`) FROM tbl_fangster WHERE `Weight` < 3 AND 
    `Date` >= '2012-04-01 00:00:00' AND `Date` <= '2012-04-30 00:00:00' 
    AND `Species` = 'Salmon') AS SumSmall 
FROM tbl_fangster 
WHERE `Date` >= '2012-04-01 00:00:00' 
AND `Date` <= '2012-04-30 00:00:00' 
AND `Species` = 'Salmon' 
GROUP BY CONCAT(WEEK(`Date`)) 

하지만 SumSmall은 매주 동일한 SumSmall 대신 SumSmall을 반환합니다. 하위 쿼리에 내 GROUP 절을 복사하려고했지만 작동하지 않았습니다.

Answer 1

CASE 문을 사용하여 다양한 조건을 처리합니다.

SELECT *, CONCAT(WEEK(`Date`)) AS Week, SUM(`Weight`) AS TotalWeight, 
     SUM(CASE WHEN Weight < 3 THEN Weight ELSE 0 END) AS SumSmall, 
     SUM(CASE WHEN Weight >= 3 AND Weight <= 7 THEN Weight ELSE 0 END) AS SumMedium, 
     SUM(CASE WHEN Weight > 7 THEN Weight ELSE 0 END) AS SumLarge 
FROM tbl_fangster 
WHERE `Date` >= '2012-04-01 00:00:00' 
AND `Date` <= '2012-04-30 00:00:00' 
AND `Species` = 'Salmon' 
GROUP BY CONCAT(WEEK(`Date`))