SQL Select 连接三个表并分组

Question

我正在尝试创建一个 SQL Select，它将查找表 #Parts 中的所有行，其中 #Parts.on_order 列中的值与实际的订购数量不匹配。这是示例。三个表：Parts、Orders 和 Receives。

IF OBJECT_ID(N'tempdb..#Parts') IS NOT NULL
BEGIN
 DROP TABLE #Parts
END
IF OBJECT_ID(N'tempdb..#orders') IS NOT NULL
BEGIN
 DROP TABLE #orders
END
IF OBJECT_ID(N'tempdb..#received') IS NOT NULL
BEGIN
  DROP TABLE #received
END

create table #Parts (part_no char(25), part_pk int, on_order decimal(12,2))
insert into #Parts (part_no, part_pk, on_order) values ('ABC1', 1, 19)
insert into #Parts (part_no, part_pk, on_order) values ('ABC2', 2, 2)
insert into #Parts (part_no, part_pk, on_order) values ('ABC3', 3, 0)

create table #orders (po_order_no int, part_no char(25), part_pk int,     qty_ordered decimal(12,2))
 insert into #orders (po_order_no, part_no, part_pk, qty_ordered) values (1, 'ABC2', 2, 10)
 insert into #orders (po_order_no, part_no, part_pk, qty_ordered) values (2, 'ABC2', 2, 1)
 insert into #orders (po_order_no, part_no, part_pk, qty_ordered) values 
 (3, 'ABC2', 2, 4   )
  insert into #orders (po_order_no, part_no, part_pk, qty_ordered) values (4, 'ABC1', 1, 20)
 insert into #orders (po_order_no, part_no, part_pk, qty_ordered) values (5, 'ABC1', 1, 6)
insert into #orders (po_order_no, part_no, part_pk, qty_ordered) values (6, 'ABC3', 3, 7)

create table #received (po_order_no int, qty_received decimal(12,2))
insert into #received (po_order_no, qty_received) values (2, 1)
insert into #received (po_order_no, qty_received) values (3, 2)
insert into #received (po_order_no, qty_received) values (4, 3)
insert into #received (po_order_no, qty_received) values (4, 2)
insert into #received (po_order_no, qty_received) values (5, 2)
insert into #received (po_order_no, qty_received) values (6, 7)

我厌倦了以下 SQL Select 但它甚至在 ORDERED 列中给了我一个错误的值：

select 
    MAX(#Parts.part_no), SUM(#received.qty_received) as RECEIVED, 
    SUM(#orders.qty_ordered) as ORDERED 
from 
    #received 
join 
    #orders on #orders.po_order_no = #received.po_order_no 
join 
    #Parts on #Parts.part_pk = #orders.part_pk 
group by 
    #Parts.part_pk, #orders.po_order_no

我错过了什么？

Answer 1

您需要考虑这样一个事实，即收到的表可以有多个记录与一个订单相关联。因此，您必须先聚合 qty_received 数据，然后再将其与订单表连接，以消除重复订单的聚合：

SELECT
    MAX(p.part_no)
    ,SUM(r.qty_received) as RECEIVED
    ,SUM(o.qty_ordered) as ORDERED
    ,SUM(o.qty_ordered) - SUM(r.qty_received) AS [DIFFERENCE]
FROM #parts AS p
JOIN #orders AS o on o.part_pk = p.part_pk
JOIN 
(   SELECT
        po_order_no
        ,SUM(qty_received) AS qty_received
    FROM #received
    GROUP BY po_order_no
) AS r on r.po_order_no = o.po_order_no
GROUP BY p.part_pk, o.po_order_no

Answer 2

创建表格：

--add # to create a temp table
CREATE TABLE Parts (
part_no CHAR(25)
,part_pk INT
,on_order DECIMAL(12, 2)
);

insert into Parts (part_no, part_pk, on_order) values 
('ABC1', 1, 19),
('ABC2', 2, 2),
('ABC3', 3, 0)

--add # to create a temp table
CREATE TABLE orders (
po_order_no INT
,part_no CHAR(25)
,part_pk INT
,qty_ordered DECIMAL(12, 2)
);

insert into orders (po_order_no, part_no, part_pk, qty_ordered) values 
(1, 'ABC2', 2, 10),
(2, 'ABC2', 2, 1),
(3, 'ABC2', 2, 4),
(4, 'ABC1', 1, 20),
(5, 'ABC1', 1, 6),
(6, 'ABC3', 3, 7)

--add # to create a temp table
CREATE TABLE received (
po_order_no INT
,qty_received DECIMAL(12, 2)
);

insert into  received (po_order_no, qty_received) values 
(2, 1),
(3, 2),
(4, 3),
(4, 2),
(5, 2),
(6, 7)

选择声明：

SELECT p.part_no
    ,SUM(r.qty_received) AS RECEIVED
    ,SUM(o.qty_ordered) AS ORDERED
    ,SUM(o.qty_ordered) - SUM(r.qty_received) AS Total_Difference
FROM (
    SELECT po_order_no
        ,sum(qty_received) AS qty_received
    FROM received
    GROUP BY po_order_no
    ) r
INNER JOIN orders o ON o.po_order_no = r.po_order_no
INNER JOIN parts p ON p.part_pk = o.part_pk
GROUP BY p.part_no, p.on_order --just need to group by part_no, on_order
    --HAVING SUM(r.qty_received) <> SUM(o.qty_ordered) --optional filter 
ORDER BY p.part_no

结果：

+---------+----------+---------+------------------+
| part_no | RECEIVED | ORDERED | Total_Difference |
+---------+----------+---------+------------------+
| ABC1    |        7 |      26 |               19 |
| ABC2    |        3 |       5 |                2 |
| ABC3    |        7 |       7 |                0 |
+---------+----------+---------+------------------+

SQL Fiddle Demo