Question

我有一张包含各种订单的表格：

ID | Date       | etc...
1  | 2013-01-01 | etc
2  | 2013-02-01 | etc
3  | 2013-03-01 | etc
4  | 2013-04-01 | etc
5  | 2013-05-01 | etc
6  | 2013-06-01 | etc
7  | 2013-06-01 | etc
8  | 2013-03-01 | etc
9  | 2013-04-01 | etc
10 | 2013-05-01 | etc

我想要一个以结果结束的查询：

overallTotal | totalThisMonth | totalLastMonth
10           | 2              | 1

但我想在一个查询中执行此操作！我试图找到一种方法来使用子查询来执行此操作。我到目前为止：

SELECT * from (
  SELECT count(*) as overallTotal from ORDERS
)

如何将其与其他子查询结合使用，以便我可以在一个查询中获得总数？

更新

最初的问题是针对MySQL，但我现在需要Firebird。

Answer 1

使用条件求和，你可以做到（MySQL语法）：

select 
    count(*) as overallTotal, 
    sum(if(Month(Date)+12*Year(Date)=Month(GetDate())+12*Year(GetDate()), 1, 0)) 
       as totalThisMonth 
    sum(if(Month(Date)+12*Year(Date)=Month(GetDate())+12*Year(GetDate())-1, 1, 0)) 
       as totalThisMonth;
from mytable

使用month+12*year公式来避免年度变化问题。

<强>更新

使用 Firebird 同样适用，您只需将Month(x)替换为EXTRACT (MONTH FROM x)，将Year(x)替换为EXTRACT (YEAR FROM x)和Getdate()与CURRENT_TIME。这看起来很难看，所以我不会把它放在这里，但你可以自己轻松做到。

Answer 2

Posubly使用IF语句结果的SUM，IF检查它是否是相关日期。

SELECT COUNT(*), 
    SUM(IF(YEAR(Date) = YEAR(CURDATE()) AND MONTH(Date) = MONTH(CURDATE()), 1, 0))
    SUM(IF((YEAR(Date) = YEAR(CURDATE()) AND MONTH(Date) = MONTH(CURDATE()) - 1) OR (YEAR(Date) = YEAR(CURDATE()) - 1 AND MONTH(Date) = 12 AND MONTH(CURDATE()) = 1), 1, 0))
from ORDERS

复杂性是由于在寻找上个月时应对年度变化而引起的

Answer 3

SELECT
  (SELECT COUNT(*) FROM C AS total) AS T,
  (SELECT COUNT(*) AS thisMonth FROM C WHERE MONTH(d) = 6) AS A,
  (SELECT COUNT(*) AS lastMonth FROM C WHERE MONTH(d) = 5) AS B;

请注意“月份”是“硬编码” - 但在应用程序级别提取“当前月份”应该不会太困难。如果你真的需要，你可以在SQL级别上使用之类的：

SELECT (SELECT COUNT(*) FROM C AS total) AS T, (SELECT COUNT(*) AS thisMonth FROM C WHERE MONTH(d) = MONTH(NOW()) ) AS A, (SELECT COUNT(*) AS lastMonth FROM C WHERE MONTH(d) = (MONTH(NOW())+11)%12) ) AS B;

Answer 4

我发现你已经在使用子查询，所以为什么不做类似下面的事情，

SELECT
(SELECT count(*) from ORDERS) as overallTotal,
(SELECT count(*) from ORDERS where Date between ... and ...) as totalThisMonth,
(SELECT count(*) from ORDERS where Date between ... and ...) as overallTotal

选择总计作为同一个表中的三个字段作为一个查询？

4 个答案: