在 Oracle 中使用子查询和按表达式分组创建视图

Question

要检索特定数据集，我必须在选择查询中使用子查询，该查询是按表达式分组的，如下所示：

SELECT SUM(b.RESERVEDROOMS) AS "Reserved Rooms",
       (SELECT country
          FROM location
         WHERE location_id = b.location_id) AS "Country"
  FROM bookingsRevenue b,
       location l
 WHERE b.location_id = l.location_id 
 GROUP BY b.location_id

它工作正常并且检索到正确的数据，但是当我尝试从中创建视图时，显示以下错误。你能帮我解决这个问题吗？

[错误] 执行 (21: 74): ORA-00979: 不是 GROUP BY 表达式

Answer 1

您的源代码似乎有些混乱。 GROUP BY 子句不正确，您也不需要使用相关子查询。 试试这个：

SELECT SUM(b.RESERVEDROOMS) AS "Reserved Rooms", l.country AS "Country"
FROM bookingsRevenue b
JOIN location l ON (b.location_id = l.location_id)
GROUP BY l.country;

如果您还希望对 location_id 进行分组，则：

SELECT SUM(b.RESERVEDROOMS) AS "Reserved Rooms", b.location_id, l.country AS "Country"
FROM bookingsRevenue b
JOIN location l ON (b.location_id = l.location_id)
GROUP BY b.location_id, l.country;