将表一的总量减去表二答案

【问题标题】：Subtracting the total quantity of table 1 to table 2将表一的总量减去表二
【发布时间】：2015-05-25 14:20:58
【问题描述】：

伙计们，我在将两个表（Deliveries 和 Returns）减去 TOTAL_QUANTITY 时遇到这个问题，这些表按 CONTAINER_TYPE 和 CUSTOMER_NAME 分组，此示例查询返回 @ 的列 Customer_Balance 987654327@ 如果我减去例如5 - 0，但如果我减去5 -1 它返回4。

select TOTAL_DELIVERY.CUSTOMER_NAME,
    TOTAL_DELIVERY.CONTAINER_TYPE,
    coalesce(TOTAL_DELIVERY.TOTAL_QUANTITY, 0) as TOTAL_DELIVERY,
    coalesce(TOTAL_PULLOUT.TOTAL_QUANTITY, 0) as TOTAL_PULLOUT,
    coalesce((TOTAL_DELIVERY.TOTAL_QUANTITY - TOTAL_PULLOUT.TOTAL_QUANTITY), 0) as CUSTOMER_BALANCE
from TOTAL_DELIVERY
left join TOTAL_PULLOUT
on TOTAL_DELIVERY.CUSTOMER_NAME = TOTAL_PULLOUT.CUSTOMER_NAME
and TOTAL_DELIVERY.CONTAINER_TYPE = TOTAL_PULLOUT.CONTAINER_TYPE


Deliveries Table (View)
================
----------------------------------------------
CUSTOMER_NAME| CONTAINER_TYPE | TOTAL_QUANTITY
-------------+----------------+---------------
Bryan        | Slim           | 5
-------------+----------------+---------------
Bryan        | Jug            | 5
-------------+----------------+---------------


Returns Table (View)
=============

CUSTOMER_NAME| CONTAINER_TYPE| TOTAL_QUANTITY
-------------+---------------+---------------
Bryan        | Slim          | 5
-------------+---------------+---------------

Expected output
===============

Customer | Container | Total_Delivery | Total_Return | Customer_Balance |
---------+-----------+----------------+--------------+------------------ 
Bryan    | Slim      | 5              | 5            | 0                |
---------+-----------+----------------+--------------+------------------
Bryan    | Jug       | 5              | 0            | 5                |
---------+-----------+----------------+---------------------------------

My INCORRECT Result output (incorrect result at the bottom right cell)
=========

Customer | Container | Total_Delivery | Total_Return | Customer_Balance |
---------+-----------+----------------+--------------+------------------ 
Bryan    | Slim      | 5              | 5            | 0                |
---------+-----------+----------------+--------------+------------------
Bryan    | Jug       | 5              | 0            | 0                |
---------+-----------+----------------+---------------------------------

你能告诉我我做错了什么吗？谢谢！

【问题讨论】：

标签： sql netbeans derby javadb

【解决方案1】：

(TOTAL_DELIVERY.TOTAL_QUANTITY - TOTAL_PULLOUT.TOTAL_QUANTITY)

必须是

(coalesce(TOTAL_DELIVERY.TOTAL_QUANTITY,0) - coalesce(TOTAL_PULLOUT.TOTAL_QUANTITY, 0))

【讨论】：