EF null字段排序后置_Sql中Null字段排在后边

落日映苍穹つ 2022-09-02 01:10 195阅读 0赞

**一、Sql中 null字段的排序处理**

null字段当做最小值，或者0，参与排序

案例：

sql：

create table NumOne(
    ID int identity(1,1),
    Num int null,
    primary key(ID)
    );
    go
    
    insert NumOne values(1);
    insert NumOne values(10);
    insert NumOne values(5);
    insert NumOne values(3);
    insert NumOne values(null);
    insert NumOne values(null);

正序排列

select * from NumOne
    order by Num;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTExMjcwMTk_size_16_color_FFFFFF_t_70][]

处理null排列

---null 列排序问题整理
    ---原理，执行两次排序
    select * from NumOne
    order by case when Num is null then 1 else 0 end asc,Num asc

![20210729152307623.png][]

**二、EF 中处理方式**

原理同上

CourseDataContext _context = new CourseDataContext();
    
    //var list = _context.NumOne.OrderBy(q => q.Num).ToList();
    
    //先判断是否为0，排序，然后根据字段后续排
    var list = _context.NumOne
        .OrderBy(q => q.Num == null)
        .ThenBy(q => q.Num)
        .ToList();
    
    foreach (var item in list)
    {
        Console.WriteLine($"id:{item.ID},num:{item.Num}");
    }

## [ EF GroupBy多个字段][EF GroupBy] ##

## [EF 根据绝对值排序处理][EF] ##

## [ EF Linq To Sql 常用查询整理\_常用使用方式整理][EF Linq To Sql] ##

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTExMjcwMTk_size_16_color_FFFFFF_t_70]: /images/20220829/7af97fcfe4964fa1adaedf10cdaf61d3.png
[20210729152307623.png]: /images/20220829/4c0fa5b4c2c44e27a213f2d3db6edf33.png
[EF GroupBy]: https://blog.csdn.net/u011127019/article/details/54943303
[EF]: https://blog.csdn.net/u011127019/article/details/88908518
[EF Linq To Sql]: https://blog.csdn.net/u011127019/article/details/114163247