使用Inner Join的SQL多表查询问题答案

【问题标题】：SQL multi table query problem using Inner Join使用Inner Join的SQL多表查询问题
【发布时间】：2020-08-10 08:27:00
【问题描述】：

我正在尝试使用 Inner Join 解决这个问题，但我不断收到错误

列出总额超过 500 美元的每个订单的客户编号、订单编号、订单日期和订单总额。将列名 ORDER_TOTAL 分配给显示订单总计的列。按订单号排序结果。

ORDERS 表有 CUSTOMER_NUM、ORDER_NUM 和 ORDER_DATE

ORDER_LINE 有 ORDER_NUM、ITEM_NUM、NUM_ORDERED 和 QOUTED_PRICE

这是我的解决方案：

SELECT CUSTOMER_NUM, ORDERS.ORDER_NUM, ORDER_DATE, SUM(QUOTED_PRICE) AS ORDER_TOTAL     
FROM ORDERS     
INNER JOIN ORDER_LINE ON ORDERS.ORDER_NUM = ORDER_LINE.ORDER_NUM    
GROUP BY ORDER_NUM     
HAVING ORDER_TOTAL > 500;

我遇到的错误：

Error starting at line : 61 in command -    
SELECT CUSTOMER_NUM, ORDERS.ORDER_NUM, ORDER_DATE, SUM(QUOTED_PRICE) AS ORDER_TOTAL     
FROM ORDERS     
INNER JOIN ORDER_LINE ON ORDERS.ORDER_NUM = ORDER_LINE.ORDER_NUM    
GROUP BY ORDER_NUM     
HAVING ORDER_TOTAL > 500

Error at Command Line : 65 Column : 8
Error report -

SQL Error: ORA-00904: "ORDER_TOTAL": invalid identifier    
00904. 00000 -  "%s: invalid identifier"

有什么建议吗？

【问题讨论】：

标签： sql oracle join group-by sum

【解决方案1】：

Oracle 不允许在GROUP BY 子句中重用SELECT 子句中定义的别名。您需要重复表达式。此外，所有非聚合列都必须出现在GROUP BY 子句中。

所以：

SELECT o.CUSTOMER_NUM, o.ORDER_NUM, o.ORDER_DATE, SUM(ol.QUOTED_PRICE) AS ORDER_TOTAL
FROM ORDERS o
INNER JOIN ORDER_LINE ol ON ol.ORDER_NUM = o.ORDER_NUM
GROUP BY o.CUSTOMER_NUM, o.ORDER_NUM, o.ORDER_DATE
HAVING SUM(ol.QUOTED_PRICE) > 500;

请注意，我修改了您的查询以使用表别名，并在每列前面加上它所属的表；这些是使查询更易于阅读和编写的良好做法，并避免了每列属于哪个表的歧义。

【讨论】：