Question

在数据库中我有：

    Name         Value
    First Player   300
    First Player   500
    First Player   250
    SecondPlayer   200
    Second Player  450

我需要向每位玩家展示最大和最小值：

Name       MaxValue   MinValue
FirstPlayer   500        250
SecondPlayer   450       200

我这样做了：

var res = (from item in _context.Players
          select item).Max(s=>s.Value);

但它只有一个具有最大值的玩家;

Answer 1

查询语法：

var result = (from item in _context.Players
group item by name into @group
select new 
{ 
    Name = @group.Key, 
    MaxValue = @group.Max(i=>i.Value), 
    MinValue = @group.Min(i=>i.Value)
}).ToList();

或者使用一个很好的linq方法语法:(这个重载基本上可以让你在“.Select()

中执行.GroupBy()”

var result = _context.Players.GroupBy(item => item.Name, (key, @group) => new
        {
            Name = key,
            MaxValue = @group.Max(i => i.Value),
            MinValue = @group.Min(i => i.Value)
        }).ToList();

Answer 2

使用Select的GroupBy应该工作：

var res = _context.Players.GroupBy(x=> x.Name)
                  .Select(x=> new 
                          { 
                                Name = x.Key, 
                                Max = x.Max(y=> y.Value), 
                                Min = x.Min(y=> y.Value) 
                          }).ToList();

或使用查询语法：

var res = (from p in _context.Players
            group p by p.Value into grp
            select new
            {
                Name = grp.Key,
                Max = grp.Max(rec => rec.Value),
                Min = grp.Min(rec => rec.Value)
            }).ToList();

使用Linq从数据库中获取Min和Max

2 个答案: