带有not in子查询子句的Sql查询到LINQ查询

问题描述

   select * from user_user_connection 
where userid_from = 3464 and 
userid_to not in
(select userid_from from 
user_user_connection 
where userid_to = 3464);

大家好，我是实体框架的新手。 我正在尝试将此查询转换为 LINQ 查询，但无法理解如何使用 not in 子句编写子查询。 另外，加入或包含哪个更好？

解决方法

这个

    from a in user_user_connection 
    join b in user_user_connection on 
        new {From=a.userid_to,To=a.userid_from} equals new {From=b.userid_from,To=b.userid_to} into c
    from d in c.DefaultIfEmpty()
    where d == null
    select a;

类似于

select a.*
from user_user_connection a
left join user_user_connection b on a.userid_to = b.userid_from and a.userid_from = b.userid_to
where b.userid_from is null

这应该与您不在查询中的匹配。

如果您想要一个特定的 userid_from，您可以添加另一个位置

    from a in user_user_connection 
    where a.userid_from == 3464
    join b in user_user_connection on 
        new {From=a.userid_to,To=b.userid_to} into c
    from d in c.DefaultIfEmpty()
    where d == null
    select a;

,

可能是这样的：

var list = userConnection.Where(user => user.useridto == 3464).Select(user => user.userid_from).ToList();
var list2 = userConnection.Where(user => !list.Contains(user.userid_to));

可能可以改进，因为包含需要相当长的时间（也许将列表放在哈希集中？）

,

这应该有效：

[routerLink]="['',{ outlets: { side-mod: ['table-list'] } }]"

或通过var query = from uc in ctx.user_user_connection where uc.userid_from = 3464 && !(from uc2 in ctx.user_user_connection where uc2.userid_to = 3464 select uc2.userid_from).Contains(uc.userid_to) select uc;

EXISTS

Ov 通过 var query = from uc in ctx.user_user_connection where uc.userid_from = 3464 && !(from uc2 in ctx.user_user_connection where uc2.userid_to = 3464 && uc.userid_to == uc2.userid_from select uc2).Any() select uc;

LEFT JOIN