LEFT加入与SUM没有显示结果，是不是在其他表

Question

站

id | name | region_id 
1 | sation1 | 1 
2 | sation2 | 1 
3 | sation3 | 2 
4 | sation4 | 2 

expenditure_heads

id | name 
1 | exp1 
2 | exp2 
3 | exp3 
4 | exp4 
5 | exp5 

expense_details

id | expenditure_head_id | station_id | year | month | expense 
1 | 1     | 1   | 2015 | 1  | 300 
2 | 2     | 1   | 2015 | 1  | 250 
3 | 3     | 1   | 2015 | 1  | 100 
4 | 4     | 1   | 2015 | 1  | 50 
5 | 5     | 1   | 2015 | 1  | 200 
6 | 1     | 3   | 2015 | 1  | 75 
7 | 2     | 3   | 2015 | 1  | 15 
8 | 3     | 3   | 2015 | 1  | 40 
9 | 4     | 3   | 2015 | 1  | 300 
10 | 5     | 3   | 2015 | 1  | 250 
11 | 1     | 3   | 2015 | 2  | 100 
12 | 2     | 3   | 2015 | 2  | 50 
13 | 3     | 3   | 2015 | 2  | 200 
14 | 4     | 3   | 2015 | 2  | 300 
15 | 5     | 3   | 2015 | 2  | 250 

我的愿望的结果让所有的站的年度报告与每个expenditure_heads的代价，我试图

SELECT exp.name AS expenditure,st.name AS station,x.totalexpense 
FROM expenditure_heads AS exp 
LEFT JOIN 
(SELECT expenditure_head_id,station_id,SUM(expense) as totalexpense 
FROM expense_details 
WHERE year = '2015' 
GROUP by expenditure_head_id,station_id 
) 
AS x ON exp.id = x.expenditure_head_id 
LEFT JOIN stations AS st ON x.station_id = st.id WHERE st.region_id=2 

此只给出站的一个正确的结果，多数民众赞成在expense_details

expenditure | station | totalexpense 
exp1  | sation3 | 175 
exp2  | sation3 | 65 
exp3  | sation3 | 240 
exp4  | sation3 | 600 
exp5  | sation3 | 500 

，但我想ID导致这样的

expenditure | station | totalexpense 
exp1  | sation3 | 175 
exp2  | sation3 | 65 
exp3  | sation3 | 240 
exp4  | sation3 | 600 
exp5  | sation3 | 500 
exp1  | sation4 | 0 
exp2  | sation4 | 0 
exp3  | sation4 | 0 
exp4  | sation4 | 0 
exp5  | sation4 | 0 

预先感谢您

Answer 1

修改查询中使用LEFT OUTER JOIN代替LEFT JOIN

SELECT exp.name AS expenditure,st.name AS station,x.totalexpense 
FROM expenditure_heads AS exp 
LEFT OUTER JOIN 
(SELECT expenditure_head_id,station_id,SUM(expense) as totalexpense 
FROM expense_details 
WHERE year = '2015' 
GROUP by expenditure_head_id,station_id 
) 
AS x ON exp.id = x.expenditure_head_id 
LEFT OUTER JOIN stations AS st ON x.station_id = st.id WHERE st.region_id=2 

你可以试试下面的查询，它可能工作：

SELECT exp.name AS expenditure,st.name AS station,x.totalexpense, exp_detail.expenditure_head_id, exp_detail.station_id, SUM(exp_detail.expense) AS totalexpense 
FROM expenditure_heads exp 
LEFT OUTER JOIN 
expense_details exp_detail ON exp_detail.year ='2015' AND exp_detail.expenditure_head_id = exp.id 
LEFT OUTER JOIN stations st ON exp_detail.station_id = st.id WHERE st.region_id=2 
GROUP by exp_detail.expenditure_head_id,exp_detail.station_id