Question

我可能已经阅读了十几个类似的主题，但我无法使用它们来解决我的问题。我很接近，可能距离解决方案只有一两步。

我有一个表，我加载的数据看起来与此类似：

CustName | Model | Serial | Color | MonthlyCount
Freds    | 123AB | L23456 | BLUE  | 987
Freds    | 123AB | L23456 | GREEN | 1127
Jimmys   | 111SS | L11234 | BLUE  | 2245
Erikas   | 123AB | L11331 | RED   | 12
Erikas   | 123AB | L11331 | BLUE  | 10
Erikas   | 123AB | L11331 | GREEN | 19

我想要的是将它们组合成一行：

CustName | Model | Serial | GreenCount | BlueCount | RedCount
Freds    | 123AB | L23456 | 987        | 1127      |
Jimmys   | 111SS | L11234 |            | 2245      |
Erikas   | 123AB | L11331 | 19         | 10        | 12

序列号是唯一的，所以我尝试使用T1.Serial = T2.Serial和T1.Serial = T3.Serial进行内部连接T1到T2和T1到T3但是我仍然得到带有NULLS的行，示例Erikas返回5行，其中只有一行包含所有数据

我尝试使用Where＆＃34; T1.MonthlyCount＆＃34;（etc）IS NOT NULL但是没有过滤任何行：

Select T1.CustName
       ,T1.Model 
       ,T1.Serial
       ,(Select T1.MonthlyCount Where T1.Color = 'BLUE') As BlueCount
       ,(Select T2.MonthlyCount Where T2.Color = 'GREEN') As GreenCount
       ,(Select T3.MonthlyCount Where T3.Color = 'RED') As RedCount
From Table1 T1

Inner Join Table2 T2
on T1.Serial = T2.Serial

Inner Join Table3 T3
on T1.Serial = T3.Serial

Where T1.MonthlyCount IS NOT NULL
AND T2.MonthlyCount IS NOT NULL
AND T3.MonthlyCount IS NOT NULL

Group By Serial, CustName, Model, Color, MonthlyCount

我得到的是：

CustName | Model | Serial | GreenCount | BlueCount | RedCount
Freds    | 123AB | L23456 | NULL       | NULL      | NULL
Freds    | 123AB | L23456 | 987        | NULL      | NULL
Freds    | 123AB | L23456 | NULL       | 1127      | NULL
Freds    | 123AB | L23456 | 987        | 1127      | NULL    <--Expected
Jimmys   | 111SS | L11234 | NULL       | NULL      | NULL
Jimmys   | 111SS | L11234 | NULL       | 2245      | NULL    <--Expected
Erikas   | 123AB | L11331 | NULL       | NULL      | NULL
Erikas   | 123AB | L11331 | 19         | NULL      | NULL
Erikas   | 123AB | L11331 | NULL       | 10        | NULL
Erikas   | 123AB | L11331 | NULL       | NULL      | 12
Erikas   | 123AB | L11331 | 19         | 10        | 12      <--Expected

我只是在寻找标记为预期的上述3行。非常感谢任何帮助。

Answer 1

使用条件聚合，并且只按您希望在每行中唯一的列进行聚合。而且，你有更多的联接而不是必要的。没有必要。

Select T1.CustName, T1.Model, T1.Serial,
       sum(case when T1.Color = 'BLUE' then t1.MonthlyCount else 0 end) As BlueCount,
       sum(case when T1.Color = 'GREEN' then t1.MonthlyCount else 0 end) As GreenCount,
       sum(case when T1.Color = 'RED' then t1.MonthlyCount else 0 end) As RedCount
From Table1 T1 
Group By T1.CustName, T1.Model, T1.Serial;

如果您想要NULL而不是0，请从每个条款中删除else 0。

Here是一个SQL小提琴，证明它有效。

Answer 2

Select T1.CustName
       ,T1.Model 
       ,T1.Serial
       ,SUM(CASE WHEN Color = 'Blue' THEN MonthlyCount ELSE 0 END) BlueCount
       ,SUM(CASE WHEN Color = 'Green' THEN MonthlyCount ELSE 0 END) GreenCount
       ,SUM(CASE WHEN Color = 'Red' THEN MonthlyCount ELSE 0 END) RedCount
From Table1 T1
Group By Serial, CustName, Model

如何在SQL中将多行合并为一行

2 个答案: