相关疑难解决方法(0)

如何为MySQL中的每个组选择第一行?

在C#中它会是这样的:

table
   .GroupBy(row => row.SomeColumn)
   .Select(group => group
       .OrderBy(row => row.AnotherColumn)
       .First()
   )
Run Code Online (Sandbox Code Playgroud)

Linq-To-Sql将其转换为以下T-SQL代码:

SELECT [t3].[AnotherColumn], [t3].[SomeColumn]
FROM (
    SELECT [t0].[SomeColumn]
    FROM [Table] AS [t0]
    GROUP BY [t0].[SomeColumn]
    ) AS [t1]
OUTER APPLY (
    SELECT TOP (1) [t2].[AnotherColumn], [t2].[SomeColumn]
    FROM [Table] AS [t2]
    WHERE (([t1].[SomeColumn] IS NULL) AND ([t2].[SomeColumn] IS NULL))
      OR (([t1].[SomeColumn] IS NOT NULL) AND ([t2].[SomeColumn] IS NOT NULL)
        AND ([t1].[SomeColumn] = [t2].[SomeColumn]))
    ORDER BY [t2].[AnotherColumn]
    ) AS [t3]
ORDER BY [t3].[AnotherColumn]
Run Code Online (Sandbox Code Playgroud)

但它与MySQL不兼容.

mysql grouping group-by

59
推荐指数
10
解决办法
12万
查看次数

标签 统计

group-by ×1

grouping ×1

mysql ×1