Question

如何将以下SQL查询（CTE LEFT JOINED与另一个表）作为Lambda或Query Expression编写？

WITH Hours as
(
    SELECT 0 As Hour
    UNION ALL
    SELECT Hour + 1
    FROM Hours
    WHERE Hour + 1 < 24
)
SELECT Hours.Hour, COALESCE(Revenue, 0) FROM Hours 
LEFT JOIN
(
SELECT DATEPART(hh, TableDate) As Hour, SUM(Revenue) Revenue FROM MyTable 
GROUP BY DATEPART(hh, TableDate)
) c
ON 
c.Hour = Hours.Hour

我知道我可以通过GroupJoin和SelectMany完成LEFT JOIN，但我不知道从哪里开始表示查询的CTE部分。我是否必须使用lambda或查询表达式创建一个静态表来实现此目的？

- 编辑 -

所以我最终得到了这个（首选查询表达式为lambda以提高可读性）：

    var revenue = (
                   from range in Enumerable.Range(0, 23)
                   join conv in db.MyTable on range equals conv.TableDate.Hour into c
                   from d in c.DefaultIfEmpty()
                   group d by range into g
                   select new { Hour = g.Key, Revenue = g.Sum(e => e == null ? 0.0 : e.Revenue), }
                  )

Answer 1

很难确切地告诉你的模型在linq中会是什么，但可能是这样的：

var Enumerable.Range(0,23)
      .Join(MyTable.GroupBy(x => x.TableDate.Hour())
             .Select(g => new { hour = g.Key, rev = g.Revenue.Sum() },
            h => h,
            g => g.hour,
            (h , g) -> new { hour = h, revenue = g.rev });

Answer 2

等效的linq查询表达式

from a in Enumerable.Range(0, 24)
join b in Mytables on a equals b.TableDate.Hour into c
from d in c.DefaultIfEmpty()
group d by a into g
select new {h = g.Key, s = g.Sum(e => e == null ? 0.0m : e.Revenue)}

LEFT JOIN CTE作为Lambda表达式/查询表达式

2 个答案: