php - MySQL SUM、ORDER BY 等

Question

我有这张 table :

我需要什么: 如果 m = '7'，则求 SUM(v+t+p)；如果 m = '8'，则求 SUM(v+t+p)，然后对其进行排序(如果 m = '8，则通过减去 (SUM(v+t+p)) ')-SUM(v+t+p) 如果 m = '7')。

Answer 1

这是您正在寻找的内容的非常普遍的形式(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
;

有几个部分可能是可选的。

更具体地说...

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: (为你的后口袋节省一些时间，希望有用)

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
;