Question

我正在尝试学习LINQ，我去了几篇有关同一问题的文章，但是无法解决这个问题。

如何在LINQ中编写以下查询？

SELECT 1
FROM A
WHERE NOT EXISTS (SELECT 1
                  FROM B
                  JOIN C ON C.id = B.c_id
                  JOIN D ON D.id = C.d_id
                  WHERE A.b_id = B.id
                    AND D.Active = 1
                  GROUP BY B.id
                  HAVING COUNT(D.id) >= 5)

编辑：我调查了Group by in LINQ，但不确定在分组依据并选择caluses之后如何访问B.c_id。我如何加入表C和D？

Answer 1

尝试以下。我使用了类以使其更容易理解

    class Program
    {
        static void Main(string[] args)
        {
            List<A> aS = new List<A>();
            List<B> bS = new List<B>();
            List<C> cS = new List<C>();
            List<D> dS = new List<D>();

            var temp = (from b in bS
                        join c in cS on b.id equals c.id
                        join d in dS on b.id equals d.id
                        select new { b = b, c = c, d = d })
                       .GroupBy(x => x.b.id)
                       .Where(x => x.Any(y => y.d.Active == 1) && (x.Count() >= 5))
                       .ToList();

            var results = aS.Where(x => !temp.Any(y => y.First().b.id == x.id)).ToList();

        }


    }
    public class A
    {
        public int id { get; set; }
    }
    public class B
    {
        public int id { get; set; }
    }
    public class C
    {
        public int id { get; set; }
    }
    public class D
    {
        public int id { get; set; }
        public int Active { get; set; }
    }

如何在多表联接的LINQ子查询中使用Group by？

1 个答案: