我在SF中已经看到过这个问题,但我是一个菜鸟,我无法让他的脑子周围的油炸。如果这感觉像是重复,请原谅我。
我的样本表
-------------------------- ID | Supplier | QTY -------------------------- 1 1 2 2 1 2 3 2 5 4 3 2 5 1 3 6 2 4
我需要获取行“UNTIL”,“QTY”的累计总数等于或大于5,按特定供应商ID的降序排列。
在此示例中,对于供应商1,它将是ID为5和2的行。
Id - unique primary key Supplier - foreign key, there is another table for supplier info. Qty - double
答案 0 :(得分:2)
它不漂亮,但我认为这样做,也许它可以成为不那么繁琐的东西的基础。请注意,我使用“假”INNER JOIN只是为了首次初始化一些变量 - 它没有任何其他角色。
SELECT ID,
supplier,
qty,
cumulative_qty
FROM
(
SELECT
ID,
supplier,
qty,
-- next line keeps a running total quantity by supplier id
@cumulative_quantity := if (@sup <> supplier, qty, @cumulative_quantity + qty) as cumulative_qty,
-- next is 0 for running total < 5 by supplier, 1 the first time >= 5, and ++ after
@reached_five := if (@cumulative_quantity < 5, 0, if (@sup <> supplier, 1, @reached_five + 1)) as reached_five,
-- next takes note of changes in supplier being processed
@sup := if(@sup <> supplier, supplier, @sup) as sup
FROM
(
--this subquery is key for getting things in supplier order, by descending id
SELECT *
FROM `sample_table`
ORDER BY supplier, ID DESC
) reverse_order_by_id
INNER JOIN
(
-- initialize the variables used to their first ever values
SELECT @cumulative_quantity := 0, @sup := 0, @reached_five := 0
) only_here_to_initialize_variables
) t_alias
where reached_five <= 1 -- only get things up through the time we first get to 5 or above.
答案 1 :(得分:0)
标准SQL没有“我能做什么行号”的概念,因此只能使用称为游标的东西来实现。使用游标编写代码就像在其他语言中使用for循环编写代码一样。
如何使用游标的示例如下:
答案 2 :(得分:0)
这个怎么样?使用两个变量。
查询:
set @tot:=0;
set @sup:=0;
select x.id, x.supplier, x.ctot
from (
select id, supplier, qty,
@tot:= (case when @sup = supplier then
@tot + qty else qty end) as ctot,
@sup:=supplier
from demo
order by supplier asc, id desc) x
where x.ctot >=5
;
| ID | SUPPLIER | CTOT |
------------------------
| 2 | 1 | 5 |
| 1 | 1 | 7 |
| 3 | 2 | 5 |
答案 3 :(得分:0)
这是关于光标的粗略演示,可能对它有帮助。
CREATE TABLE #t
(
ID INT IDENTITY,
Supplier INT,
QTY INT
);
TRUNCATE TABLE #t;
INSERT INTO #t (Supplier, QTY)
VALUES (1, 2),
(1, 2),
(2, 5),
(3, 2),
(1, 3);
DECLARE @sum AS INT;
DECLARE @qty AS INT;
DECLARE @totalRows AS INT;
DECLARE curSelectQTY CURSOR
FOR SELECT QTY
FROM #t
ORDER BY QTY DESC;
OPEN curSelectQTY;
SET @sum = 0;
SET @totalRows = 0;
FETCH NEXT FROM curSelectQTY INTO @qty;
WHILE @@FETCH_STATUS = 0
BEGIN
SET @sum = @sum + @qty;
SET @totalRows = @totalRows + 1;
IF @sum >= 5
BREAK;
END
SELECT TOP (@totalRows) *
FROM #t
ORDER BY QTY DESC;
CLOSE curSelectQTY;
DEALLOCATE curSelectQTY;
答案 4 :(得分:0)
SELECT x.*
FROM supplier_stock x
JOIN supplier_stock y
ON y.supplier = x.supplier
AND y.id >= x.id
GROUP
BY supplier
, id
HAVING SUM(y.qty) <=5;