Question

好的，首先，我要更改表格，字段和值的名称，我只是保留数据库的结构供您理解。

现在，让我们假设我有一个表people，其中包含字段id，age，country和language。另一张表格foods，其中包含每个人在people吃饭的食物，字段：person_id，food，units。注意：food是char，而不是另一个表的ID，我无法更改此结构。

现在，让我们提供一些数据：

人

ID | AGE | COUNTRY | LANGAGE
1  |  25 |   usa   |  en
2  |  46 |   mex   |  es

食品

ID | PERSON_ID | FOOD  | UNITS
1  |     1     | apple |   2
2  |     1     | grape |  24
3  |     1     | pizza |   1
4  |     2     | apple |   3
5  |     2     | pizza |   2

很好，我需要的是获取id，age，country以及某人吃掉的apple和grape的总和（忽略pizza）。在这个例子中，如果我寻找ID 1，我应该得到：

ID | AGE | COUNTRY | UNITS 
1  |  25 |   usa   | 26

对于ID 2：

ID | AGE | COUNTRY | UNITS 
2  |  46 |   mex   | 3

Answer 1

select p.id, p.age, p.country, sum(f.units) as units
from people p join foods f
on (p.id = foods.person_id and f.food in ('apple', 'grape'))
group by p.id, p.age, p.country

如果您需要其他食物组合，只需编辑in条款的内容。

Answer 2

http://sqlfiddle.com/#!9/38304/2

SELECT p.*, SUM(f.units)
FROM people p
LEFT JOIN foods f
ON f.person_id = p.id
  AND f.food in('apple','grape')
GROUP BY p.id

Answer 3

SELECT p.Id, p.Age,p.country, sum(f.units)
FROM people AS p
INNER JOIN foods AS f ON f.person_id = p.id
WHERE f.food <> 'Pizza'
GROUP BY p.id,p.age,p.country

Answer 4

select p.id, p.age, p.country, sum(f.units) as units 
from people p 
join foods f on f.person_id = p.id 
where f.food <> 'Pizza' 
group by p.id, f.food

Answer 5

select 
t1.id, t1.age, t1.country, sum(t2.units)
from people as t1, foods as t2
where 
t1.id = t2.person_id and t2.food != 'pizza'
group by t1.id 
order by t1.id

关于MySQL的总和左连接关系1：X

人

食品

5 个答案: