Question

我有一个像这样的MySQL查询：

SELECT *, SUM(...some SQL removed for brevety) AS Occurrences FROM some_table AS q
WHERE criterion="value" GROUP BY q.P_id ORDER BY Occurrences DESC LIMIT 10;

我想将结果限制为出现次数> 0的行。这对我来说似乎很简单，但我似乎无法使其发挥作用。无论我尝试什么，WHERE或HAVING，每当我尝试添加这个限制时，我得到NO ROWS作为回报。我很肯定我的表中有数据应该返回。有谁知道如何完成我正在做的事情？

我试过这个，但它仍然不起作用。任何想法为什么它仍然不起作用？

SELECT *, SUM(...some SQL removed for brevety) AS Occurrences FROM some_table AS q
WHERE criterion="value" HAVING SUM(...some SQL removed for brevety)>0 GROUP BY q.P_id ORDER BY Occurrences DESC LIMIT 10;

Answer 1

我对MySQL的熟悉程度与SQL Server不同，但在T-SQL中，你不能在GROUP BY子句中使用别名（我最初也认为是ORDER BY子句，但是后来证明了不正确）。在这种情况下，您希望根据GROUP BY的结果进行过滤，因此我将使用HAVING子句，如下所示：

SELECT *, SUM(... some SQL removed for brevity ...) AS Occurrences
FROM
    some_table AS q
WHERE
    criterion = 'value'
GROUP BY
    q.P_id
HAVING
    SUM(... some SQL removed for brevity ...) > 0
ORDER BY
    Occurrences DESC
LIMIT 10;

Answer 2

此查询适用于我......

select order_id, sum(qty_ordered) as total_qty 
from sales_flat_order_item 
group by order_id 
having total_qty > 10
order by total_qty desc

Answer 3

啊，我找到了适合它的地方。

声明现在是：

SELECT *, SUM(...some SQL removed for brevety) AS Occurrences FROM some_table AS q
WHERE criterion="value" GROUP BY q.P_id HAVING SUM(...some SQL removed for brevety)>0 ORDER BY Occurrences DESC LIMIT 10;

ORDER BY Occurrences似乎工作得很好，

Answer 4

根据SQL标准，列别名在查询正文中不可用，这是一个混乱的麻烦。鉴于您的尝试，听起来好像MySQL（和其他一些DBMS）也是如此。您可能必须在ORDER BY子句中重复该表达式。

此外，GROUP BY子句应列出*中的每一列，而不仅仅是主键（但从逻辑上讲，指定主键应该足够）。

Answer 5

我认为聚合应该在HAVING子句中。但诚然，我不确定是否接受了别名。

HAVING (Occurrences > 0)

HAVING (SUM(...some SQL removed for brevety) > 0)

或者，您可以使用子查询：

SELECT *
FROM (
   -- your current query
) AS sub
WHERE (Occurences > 0)

如何在MySQL WHERE子句中使用别名列？

5 个答案: