table1的总量减去table2

Question

伙计们，我在用CONTAINER_TYPE和CUSTOMER_NAME分组的TOTAL_QUANTITY减去两个表（Deliveries和Returns）时遇到了这个问题，此示例查询 returns 0 的列 Customer_Balance 如果我减去例如 5 - 0，但如果我减去 5 -1 它 returns 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！

Answer 1

(TOTAL_DELIVERY.TOTAL_QUANTITY - TOTAL_PULLOUT.TOTAL_QUANTITY)

必须是

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

table1的总量减去table2

Subtracting the total quantity of table 1 to table 2

sql

netbeans

derby

javadb