Question

我们有一个MySQL数据库，它有两个表，Warehouse和Crate

Warehouse:
WarehouseID (primary key)
Location (varchar)

Crate:
CrateID (primary key)
Warehouse (foreign key to a Warehouse record)
Max_Capacity (int) (the amount of boxes that can be packed into a crate)

我想编写一个查询，返回每个仓库的所有包装箱的max_capacity的总和。我遇到了重复条目和内连接的问题，所以我希望的是：

LOCATION:    WAREHOUSE_ID:  TOTAL_CAPACITY:
Shoreline    1              60
Bellevue     2              120
Ballard      3              200

每个仓库可能有10个左右的箱子。

Answer 1

select w.location, w.warehouse_id, sum(c.capacity) as total_capacity 
from warehouse w, crate c 
where w.warehouse_id = c.warehouse_id 
group by c.warehouse_id

Answer 2

你应该查看mysql手册中的这些词：

内部联接
group by
总和（）

这些可以帮助您组装所需的查询。

Answer 3

只是仓库分组：

（假设crate表中的外键名为warehouseID）

SELECT 
  warehouse.location, 
  warehouse.warehouseID, 
  SUM(crate.max_capacity) AS total_capacity
FROM warehouse
INNER JOIN crate
  ON crate.warehouseID = warehouse.warehouseID
GROUP BY
  warehouse.warehouseID

MySQL查询 - 汇总多个仓库的容量

3 个答案: