Question

让我说我有这个查询：

SELECT id, date, amount, cancelled
FROM transactions

哪个给我以下结果：

id  date     amount   ref
1   01/2019  5.00     a
1   02/2019  10.00    b
1   06/2019  20.00    c
2   10/2019  11.00    d

如果有重复的ID，我该如何获取一个具有最新日期，所有金额之和和一个所有字符串的串联字符串的ID引用字段？即：

id  date     amount   ref
1   06/2019  35.00    abc
2   10/2019  11.00    d

这里是使用最大日期获取不同ID的SQL，但我不确定如何汇总数量/参考字段

WITH data_with_date_sequence AS (
    SELECT
          id
        , date
        , amount
        , ref
        , ROW_NUMBER() OVER(PARTITION BY id ORDER BY date DESC) AS seq
    FROM dbo.SomeTable
)
SELECT
      id
    , date
    , amount
    , ref
FROM data_with_date_sequence
WHERE seq = 1;

Answer 1

对于此用例，我看不到需要窗口函数。请考虑以下聚合查询：

select 
    id, 
    max(date) date, 
    sum(amount) amount,
    string_agg(ref, '') within group (order by date) ref
from mytable
group by id

注意：string_agg()是在SQL Server 2017中添加的。

Answer 2

将public class Item : INotifyPropertyChanged { public string Title { get; set; } // TODO: Notify on change public bool VisibleSelf { get; set; } // TODO: Notify on change public bool VisibleChildOrSelf { get; set; } // TODO: Notify on change public ObservableCollection<Item> Items { get; set; } // TODO: Notify on change public void CheckVisibility(string searchText) { VisibleSelf = // Title contains SearchText. You may use RegEx with wildcards VisibleChildOrSelf = VisibleSelf; foreach (var child in Items) { child.CheckVisibility(searchText); VisibleChildOrSelf |= child.VisibleChildOrSelf; } } } public class ViewModel : INotifyPropertyChanged { public ObservableCollection<Item> Source { get; set; } // TODO: Notify on change public string SearchText { get; set; } // TODO: Notify on change private void OnSearchTextChanged() // TODO: Action should be delayed by 500 millisec { foreach (var item in Source) item.CheckVisibility(SearchText); } } <StackPanel> <TextBox Text="{Binding SearchText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" MinWidth="200" Margin="5"/> <TreeView ItemsSource="{Binding Source}" Margin="5"> <TreeView.ItemTemplate> <HierarchicalDataTemplate ItemsSource="{Binding Items}"> <TextBlock Text="{Binding Title}" /> </HierarchicalDataTemplate> </TreeView.ItemTemplate> <TreeView.ItemContainerStyle> <Style TargetType="Control"> <Style.Triggers> <DataTrigger Binding="{Binding VisibleChildOrSelf}" Value="false"> <Setter Property="Visibility" Value="Collapsed"/> </DataTrigger> <DataTrigger Binding="{Binding VisibleSelf}" Value="false"> <Setter Property="Foreground" Value="Gray"/> </DataTrigger> </Style.Triggers> </Style> </TreeView.ItemContainerStyle> </TreeView> <StackPanel>与window function一起使用：

sum()

如果您使用的是最新版本，则可以使用STRING_AGG()。

这里是demo。

将ROW_NUMBER（）与聚合函数一起使用

2 个答案: