用Sql语句查询库存

create table table1(
name char(50),
total int
)

insert into table1 (name,total) values('A',200);
insert into table1 (name,total) values('B',1000);

mysql> select * from table1;
+------+-------+
| name | total |
+------+-------+
| A | 200 |
| B | 1000 |
+------+-------+
2 rows in set (0.00 sec)

create table table2(
name char(50),
number int
)

insert into table2 (name,number) values('A',20);
insert into table2 (name,number) values('A',80);
insert into table2 (name,number) values('B',100);
insert into table2 (name,number) values('B',200);

mysql> select * from table2;
+------+--------+
| name | number |
+------+--------+
| A | 20 |
| A | 80 |
| B | 100 |
| B | 200 |
+------+--------+
4 rows in set (0.00 sec)

select aa.name,(aa.total-cc.total1)as sub

　　 from table1 aa,(select sum(number)as total1 from table2 group by name) cc

　　group by name;

查询库存结果为：

+------+------+
| name | sub |
+------+------+
| A | 100 |
| B | 900 |
+------+------+
2 rows in set (0.00 sec)