Question

在表A中我有日期，而在B中我有订单号。在这两个表中，我有一个称为订单ID的公共字段。我只有一个简单的目标来获取每个日期的订单数量[如第1，第2 ..] 这是我尝试过的，因为我不想使用连接或视图。

select 
A.date_of_order,
count(B.order_number)
from A, B
where A.order_id=B.order_id;
group by A.date_of_order

我收到以下错误。可能会犯一些微不足道的错误。提前致谢更新：考虑到Dmitri和rafa的建议后，我得到了表格：

23-FEB-14   1
23-FEB-14   1
23-FEB-14   2
23-FEB-14   2
23-FEB-14   2
07-MAR-14   2
07-MAR-14   4
07-MAR-14   1
07-MAR-14   5
02-MAR-14   1
02-MAR-14   1

正如我所说，我的要求非常简单，只需将其作为

23-Feb-14 10[i.e. all the orders placed on this date]
07-Mar-14 13
02-mar-14 2

Answer 1

在 GROUP BY：

之前应该放
select A.date_of_order, count(B.order_number) from A, B where A.order_id = B.order_id -- <- possible, but join will be better here group by A.date_of_order

如果你想在 GROUP BY之后找到条件，你应该使用HAVING

select A.date_of_order, count(B.order_number) from A, B where A.order_id = B.order_id group by A.date_of_order having count(B.order_number) < 3 -- having demo

Answer 2

WHERE子句必须在GROUP BY子句的之前。使用TRUNC(date)摆脱时间，以便GROUP BY按预期工作。

SELECT TRUNC(A.date_of_order), COUNT(B.order_number) FROM A, B WHERE A.order_id=B.order_id GROUP BY TRUNC(A.date_of_order)

无论如何，建议改为使用ANSI-standard SQL JOIN子句。

SELECT TRUNC(A.date_of_order), COUNT(B.order_number) FROM A INNER JOIN B ON A.order_id = B.order_id -- (WHERE conditions here) GROUP BY TRUNC(A.date_of_order) -- (HAVING conditions here)

Answer 3

可能的原因可能是

1）日期有时间戳，在这种情况下，查询后会有所帮助：

select 
trunc(A.date_of_order),
count(B.order_number)
from A, B
where A.order_id=B.order_id
group by trunc(A.date_of_order);

2）因为在您的示例数据中，您已经计算了日期，所以您需要为查询计算总和而不是计数

select 
A.date_of_order,
sum(B.order_number)
from A, B
where A.order_id=B.order_id
group by A.date_of_order;

3）或者可以两者兼而有，在这种情况下你可以尝试

select 
trunc(A.date_of_order),
sum(B.order_number)
from A, B
where A.order_id=B.order_id
group by trunc(A.date_of_order);

Answer 4

我根本不明白为什么你需要加入另一张桌子。试着跑步：

select date_of_order, count(order_id) from tbl_a group by date_of_order

您的问题表明，表A包含每个订单ID和日期的行，您想要做的就是按日期计算订单数。

使用group by时出错

4 个答案: