MySQL SUM，ORDER BY等

Question

我有这张桌子：

我需要什么： SUM（v + t + p），如果m =＆＃39; 7＆＃39;和SUM（v + t + p），如果m =＆＃39; 8＆＃39;，并对其进行排序（通过减去（SUM（v + t + p），如果m =＆＃39; 8＆＃39;） - SUM （v + t + p）如果m =＆＃39; 7＆＃39;）。

Answer 1

这是你正在寻找的一般形式（可能）：

SELECT [somestuff?] 
, SUM(IF([condition1], [calculation1], 0) AS X1
, SUM(IF([condition2], [calculation2], 0) AS X2
FROM theTable
WHERE [something]
GROUP BY [something else]
ORDER BY X1 - X2
;

您可以选择多个部分。

更具体......

SELECT SUM(IF(m = '8', v+t+p, 0) AS sum8
, SUM(IF(m = '7', v+t+p, 0) AS sum7
FROM theTable
ORDER BY sum8-sum7  // This ORDER BY won't really do anything; 
                    // there is only one row since we didn't 
                    // GROUP BY anything
;

编辑： （为你的后兜节省一些时间，希望有用的东西）

create table thing
(   id int auto_increment primary key,
    n int not null,
    m int not null,
    v int not null,
    t int not null,
    p int not null
);

insert thing(n,m,v,t,p) values (2,8,0,0,0);
insert thing(n,m,v,t,p) values (14,8,0,0,0);
insert thing(n,m,v,t,p) values (48,7,123,123,123);
insert thing(n,m,v,t,p) values (48,8,12,1,2);
insert thing(n,m,v,t,p) values (390,8,0,0,0);

编辑：

SELECT n
, SUM(IF(m = '8', v+t+p, 0) AS sum8
, SUM(IF(m = '7', v+t+p, 0) AS sum7
, SUM(IF(m = '8', v+t+p, 0)
  - SUM(IF(m = '7', v+t+p, 0) AS sumDiff
FROM the_table
GROUP BY n
ORDER BY sumDiff
;