如何查询SUM连接表？

Question

我不知道标题应该如何。对标题的思考比写这个问题需要更多的时间。
给点
假设我有三个表：

//table customers 
| ID | Name     | 
++++++++++++++++++++++++++++++++ 
| 194 | PT Comro Haneut  | 
| 195 | PT Kareueut Kameumeut | 

//table customer's savings 
| ID | IDCustomer | SavingsAmount | 
+++++++++++++++++++++++++++++++++++++ 
| 1 | 194  | 5000000 | 
| 2 | 195  |  250000 | 
| 3 | 195  | 2500000 | 
| 4 | 194  |  125000 | 
| 5 | 194  |  175000 | 

//table transactions 
| ID | IDCustomer | Amount  | 
+++++++++++++++++++++++++++++++++++++ 
| 1 | 195  | 1000000 | 
| 2 | 195  |  250000 | 
| 3 | 194  | 3500000 | 
| 4 | 194  |  300000 | 

目标
我要总结的储蓄金额和交易量，并且使结果在一行，像这样：

// expected result of the query 
| IDCustomer | Savings  | Transactions | Balance  | 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 
| 194  | 5300000 | 4800000  | 500000  | 
| 195  | 2750000 | 1250000  | 1500000  | 

我试图建立由我自己的查询，但我总是失败。我得到的储蓄和交易总额增加了一倍。

任何人都可以帮忙吗？

Answer 1

查询

select svg.id, Savings, Transactions, (Savings - Transactions) as Balance 
from 
(
    select c.id as id, sum(s.SavingsAmount) as Savings 
    from customers c 
    inner join savings s 
    on c.id=s.idcustomer 
    group by c.id 
) svg 
inner join 
(
    select c.id as id, sum(t.amount) as Transactions 
    from customers c 
    inner join transactions t 
    on c.id=t.idcustomer 
    group by c.id 
) trans 
on svg.id = trans.id 
; 

设置

create table customers 
(
    id integer primary key not null, 
    name varchar(23) not null 
); 

create table savings 
(
    id integer primary key not null, 
    IDCustomer integer not null, 
    SavingsAmount decimal(10, 2) not null, 
    foreign key (IDCustomer) references customers (id) 
); 

create table transactions 
(
    id integer primary key not null, 
    IDCustomer integer not null, 
    amount decimal(10, 2) not null, 
    foreign key (IDCustomer) references customers (id) 
); 

insert into customers 
(id, name) 
values 
(194 , 'PT Comro Haneut'  ), 
(195 , 'PT Kareueut Kameumeut') 
; 

insert into savings 
( id , IDCustomer , SavingsAmount) 
values 
( 1 , 194  , 5000000 ), 
( 2 , 195  ,  250000 ), 
( 3 , 195  , 2500000 ), 
( 4 , 194  ,  125000 ), 
( 5 , 194  ,  175000 ) 
; 

insert into transactions 
( id , IDCustomer , amount  ) 
values 
( 1 , 195  , 1000000 ), 
( 2 , 195  ,  250000 ), 
( 3 , 194  , 3500000 ), 
( 4 , 194  ,  300000 ) 
; 

---

输出

+-----+------------+--------------+------------+ 
| id | Savings | Transactions | Balance | 
+-----+------------+--------------+------------+ 
| 194 | 5300000.00 | 3800000.00 | 1500000.00 | 
| 195 | 2750000.00 | 1250000.00 | 1500000.00 | 
+-----+------------+--------------+------------+ 

sqlfiddle

Answer 2

看起来你并不需要从客户表中的任何具体数据，所以才来优化你可以使用结果

SELECT savings.IDCustomer, sum(SavingsAmount) as savings,sum(Amount) as amount, sum(SavingsAmount)-sum(Amount) as Balance 
FROM savings 
LEFT JOIN transactions 
ON savings.IDCustomer=transactions.IDCustomer 
group by savings.IDCustomer 
ORDER BY savings.IDCustomer;