Question

假设我在Sql中有以下查询

select UserID,count(distinct ip) as NumberOfIPUsed from  UserLogs 
group by UserID

我希望它与Linq一起写

Answer 1

好吧，首先，您要按UserID分组：

UserLogs.GroupBy(ul => ul.UserID)

然后，您要获取用户ID和与此不同的ip的数量：

UserLogs.GroupBy(ul => ul.UserID).Select(g => new {UserID = g.Key, Count = g.Select(ul => ul.ip).Distinct().Count()})

Answer 2

您需要使用Distinct函数，该函数在理解表达式中不直接可用，因此需要某些函数样式：

var res = await (from ul in context.UserLogs
                 group ul by ul.UserId into grouped
                 select new {
                   UserId = grouped.Key,
                   Count = group.Select(x => x.ip).Distinct().Count()
                 }).ToListAsync();

如何在Linq中编写非重复计数查询

2 个答案: