选择总计作为同一个表中的三个字段作为一个查询？

Question

I have a table with various orders in it:

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

I want a query that ends wit the result:

overallTotal | totalThisMonth | totalLastMonth
10           | 2              | 1

But I want to do this in one query! I am trying to find a way to use subqueries to do this. SO far I have:

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

How can I combine this with other subqueries so I can get the totals in one query?

UPDATE

Original question was for MySQL, but I need it for Firebird now.

Answer 1

With conditional sums you can do it (MySQL syntax):

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

Use the month+12*year formula to avoid the problem with year change.

UPDATE

With Firebird the same applies, you only have to replace Month(x) with EXTRACT (MONTH FROM x) , Year(x) with EXTRACT (YEAR FROM x) and Getdate() with CURRENT_TIME . This will look ugly, so I won't put it here, but you could easily do it yourself.

Answer 2

Posubly use SUM of the result of IF statements, with the IF checking that it is a relevant date.

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

Complexity is caused by coping with a change of year when looking for the previous month

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;

Please notice "month" are "hard coded" -- but it shouldn't be too difficult to extract the "current month" at application level. If you really need to, you could do it at SQL level with something like that:

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

I see you are already using sub queries, so why not do something like the following,

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