使用多个连接查找最小值

Question

我在 BigQuery 中使用 StandardSQL，并且有 7 个表，每个表有 10 到 75 列和数千行。为简单起见，我只会将相关的表和列用于我想要完成的任务。

表 1

Item	Desc
12341	abcd
23451	bcda
34561	cdab
45671	dabc

表 2

SubItem	Location	ON_OFF	OnHand	OnOrder
12345	1	ON	3	5
12345	2	ON	4	2
12345	3	ON	2	4
12346	1	ON	7	7
12346	2	ON	1	4
12346	3	ON	8	7
23451	1	OFF	1	1
23451	2	OFF	3	2
34567	1	ON	6	0
34567	2	ON	1	5
34568	1	ON	2	0
34568	2	ON	3	10
45671	2	ON	5	1

表 3

Item	SubItem
12341	12346
23451	23451
34561	34567
34561	34568

当前结果

Item	Desc	ON_OFF	OH	OO
12341	abcd	ON	9	11
12341	abcd	ON	16	18
23451	bcda	OFF	4	3
34561	cdab	ON	7	5
34561	cdab	ON	5	10
45671	dabc	ON	5	1

想要的结果

Item	Desc	ON_OFF	OH	OO
12341	abcd	ON	9	18
23451	bcda	OFF	4	3
34561	cdab	ON	5	5
45671	dabc	ON	5	1

我正在寻找每个项目的最小 OH 和最小 OO 值，与项目 45671 的情况一样，这与相同的子项目编号不对应。

为我提供当前结果表的当前代码是：

Select 
Table1.Item,
Table1.Desc,
Table2.ON_OFF,
Table2.OH,
Table2.OO
From Table1
Left Join Table3
On Table1.Item = Table3.Item
Left Join 
    (Select SubItem, ON_OFF, Sum(OnHand) As OH, Sum(OnOrder) As OO
        From Table 2
        Group by 1,2)
ON Table3.SubItem = Table2.SubItem;

寻找想法，因为我对 SQL 还很陌生，当前的实际代码将 7 个表与各种连接联系起来，以构建一个包含 45 列和数千行的最终表。我看过使用 RowNumber() 和 Partition By，但我不确定它会去哪里。还考虑将 OO 和 OH 分成两个连接可能会有所帮助。

欢迎提出任何建议！谢谢！

Answer 1

查看您的示例数据，您似乎可以使用group by 和聚合函数min，如下所示：

Select Table1.Item,
       Table1.Desc,
       Table2.ON_OFF,
       Min(Table2.OH),
       Min(Table2.OO)
  From Table1
  Left Join Table3
    On Table1.Item = Table3.Item
  Left Join (Select SubItem,
                    ON_OFF, 
                    Sum(OnHand) As OH,
                    Sum(OnOrder) As OO
               From Table2
              Group by 1,2) Table2
    ON Table3.SubItem = Table2.SubItem
Group by Table1.Item, Table1.Desc, Table2.ON_OFF;

Answer 2

在得到一些急需的睡眠后，我开始使用它......

我想出了下面的，它正在工作！

SELECT T1.Item, 
 T1.Desc,
 T3_1.ONOFF, 
 T3_1.OH,
 T3_2.OO
 FROM Table1 T1

 Left Join
    (Select Item, SubItem,T2_1.O_O as ONOFF, T2_1.OH1 as OH,
    ROW_NUMBER() OVER(PARTITION BY Item ORDER BY T2_1.OH1) as rn
    FROM T2_1
    Left Join
      (Select SubItem, SUM(IFNULL(OnHand,0)) AS OH1,
      FROM  Table2 
      GROUP BY 1) T2_1
    ON T2_1.SubItem = T3_1.SubItem) T3_1
  On T1.Item = T3_1.Item
  
 Left Join
    (Select Item, SubItem, T2_2.OO1 as OO,
    ROW_NUMBER() OVER(PARTITION BY Item ORDER BY T2_2.OO1) as rn2
    FROM T2_2
    Left Join
      (Select SubItem, SUM(IFNULL(OnOrder,0)) AS OO1,
      FROM  Table2 
      GROUP BY 1) T2_2
    ON T2_2.SubItem = T3_2.SubItem) T3_2
  On T1.Item = T3_2.Item
 
 Where rn = 1 and rn2 = 1;

谢谢！