mysql - 多个帐户的总和值

Question

我正在尝试计算销售额的总和。但是，一个用户可以有多个账户，每个账户有不同的销售记录。下面是我的表格。

用户表

user_id username
----------------
1       adam   
2       david
3       siva    

帐户

account user_id
-------------
001     1       
002     1       
003     1       

销售

account sales
-------------
001     20      
002     30      
003     10    

如何汇总一个用户的所有销售额？请帮我。谢谢

Answer 1

mysql> create table user_table(user_id int, username varchar(20));
Query OK, 0 rows affected (0.45 sec)

mysql> insert into user_table values
    -> (1,'adam'),
    -> (2,'david'),
    -> (3,'siva'); 
Query OK, 3 rows affected (0.10 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> 
mysql> create table account(account varchar(20), user_id int);
Query OK, 0 rows affected (0.34 sec)

mysql> insert into account values
    -> ('001',1),       
    -> ('002',1),
    -> ('003',1);
Query OK, 3 rows affected (0.06 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> 
mysql> create table sales(account varchar(20),sales int);
Query OK, 0 rows affected (0.26 sec)

mysql> insert into sales values
    -> ('001',20),      
    -> ('002',30),
    -> ('003',10);
Query OK, 3 rows affected (0.12 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select u.user_id,sum(sales) sales
    -> from user_table u
    -> natural join account
    -> natural join sales
    -> where u.user_id = 1; 
+---------+-------+
| user_id | sales |
+---------+-------+
|       1 |    60 |
+---------+-------+
1 row in set (0.00 sec)