Linq(MIN && MAX)

Question

什么等于LINQ中的sql以下

select MIN(finishTimestamp) AS FromDate, MAX(finishTimeStamp) AS ToDate From Transactions

??

from t in Transactions
select new {
          FromDate = ?,
          ToDate = ?
        }

谢谢

Answer 1

要在Linq to SQL中使用多个聚合,在表上没有分组,我发现避免进行多个查询的唯一方法是创建一个" 假组 ":

 var q = from tr in dataContext.Transactions
         group tr by 1 into g // Notice here, grouping by a constant value
         select new
         {
           FromDate = g.Min(t => t.InvoiceDate),
           ToDate = g.Max(t => t.InvoiceDate)
         };

有点hacky,但生成的SQL是干净的,通过这样做,您只对数据库进行一次查询.

Answer 2

你可以这样做

var transactionDates = from t in Transactions 
                       select t.FinishTimeStamp;

var dates = new { 
                   FromDate = transactionDates.Min(), 
                   ToDate = transactionDates.Max() 
                };