>我用 LINQ 创建了以下查询：
var today = DateTime.Today;
var month = new DateTime(today.Year, today.Month, 1);
var first = month.AddMonths(-1);
var last = month.AddDays(-1);
var baseQuery = (from jr in DollarU_JobRuns
where (jr.Day >= first && jr.Day <= last)
group jr by new { System = jr.SYSU.Substring(0, 2) }
into systemGroup
let NbrOfJobRunsSucceeded = systemGroup.Sum(x => x.NbrOfJobRunsSucceeded)
let NbrOfJobRunsFailed = systemGroup.Sum(s => s.NbrOfJobRunsFailed)
select new
{
System = systemGroup.Key.System,
NbrOfJobRunsSucceeded,
NbrOfJobRunsFailed,
Total = NbrOfJobRunsSucceeded + NbrOfJobRunsFailed
}).OrderByDescending(item => item.Total);
var query = baseQuery.Take(10).Concat(
baseQuery.Skip(10).Select(item => new
{
System = "Others",
NbrOfJobRunsSucceeded = item.NbrOfJobRunsSucceeded,
NbrOfJobRunsFailed = item.NbrOfJobRunsFailed,
Total = item.NbrOfJobRunsSucceeded + item.NbrOfJobRunsFailed,
}
)
)
.GroupBy(g => g.System)
.Select(
g => new
{
System = g.Key,
NbrOfJobRunsSucceeded = g.Sum(x => x.NbrOfJobRunsSucceeded),
NbrOfJobRunsFailed = g.Sum(x => x.NbrOfJobRunsFailed),
Total = g.Sum(x => x.Total)
}
)
.OrderByDescending(item => item.Total);
query.Dump();
这将生成以下 SQL 查询：
SELECT
[Project9].[C5] AS [C1],
[Project9].[C4] AS [C2],
[Project9].[C1] AS [C3],
[Project9].[C2] AS [C4],
[Project9].[C3] AS [C5]
FROM ( SELECT
[GroupBy5].[A1] AS [C1],
[GroupBy5].[A2] AS [C2],
[GroupBy5].[A3] AS [C3],
[GroupBy5].[K1] AS [C4],
1 AS [C5]
FROM ( SELECT
[UnionAll1].[C1] AS [K1],
SUM([UnionAll1].[C2]) AS [A1],
SUM([UnionAll1].[C3]) AS [A2],
SUM([UnionAll1].[C4]) AS [A3]
FROM (SELECT TOP (10)
[Project3].[C2] AS [C1],
[Project3].[C1] AS [C2],
[Project3].[C4] AS [C3],
[Project3].[C3] AS [C4]
FROM ( SELECT
[Project2].[C1] AS [C1],
[Project2].[C2] AS [C2],
[Project2].[C1] + [Project2].[C3] AS [C3],
[Project2].[C3] AS [C4]
FROM ( SELECT
[Project1].[C1] AS [C1],
[Project1].[C2] AS [C2],
(SELECT
SUM([Extent2].[NbrOfJobRunsFailed]) AS [A1]
FROM [dbo].[DollarU_JobRuns] AS [Extent2]
WHERE ([Extent2].[Day] >= '2017-09-01') AND ([Extent2].[Day] <= '2017-09-30') AND (([Project1].[C2] = (SUBSTRING([Extent2].[SYSU], 0 + 1, 2))) OR (([Project1].[C2] IS NULL) AND (SUBSTRING([Extent2].[SYSU], 0 + 1, 2) IS NULL)))) AS [C3]
FROM ( SELECT
[GroupBy1].[A1] AS [C1],
[GroupBy1].[K1] AS [C2]
FROM ( SELECT
[Filter1].[K1] AS [K1],
SUM([Filter1].[A1]) AS [A1]
FROM ( SELECT
SUBSTRING([Extent1].[SYSU], 0 + 1, 2) AS [K1],
[Extent1].[NbrOfJobRunsSucceeded] AS [A1]
FROM [dbo].[DollarU_JobRuns] AS [Extent1]
WHERE ([Extent1].[Day] >= '2017-09-01') AND ([Extent1].[Day] <= '2017-09-30')
) AS [Filter1]
GROUP BY [K1]
) AS [GroupBy1]
) AS [Project1]
) AS [Project2]
) AS [Project3]
ORDER BY [Project3].[C3] DESC
UNION ALL
SELECT
[Project7].[C3] AS [C1],
[Project7].[C1] AS [C2],
[Project7].[C5] AS [C3],
[Project7].[C4] AS [C4]
FROM ( SELECT
[Project6].[C1] AS [C1],
[Project6].[C1] + [Project6].[C2] AS [C2],
N'Others' AS [C3],
[Project6].[C1] + [Project6].[C2] AS [C4],
[Project6].[C2] AS [C5]
FROM ( SELECT
[Project5].[C1] AS [C1],
(SELECT
SUM([Extent4].[NbrOfJobRunsFailed]) AS [A1]
FROM [dbo].[DollarU_JobRuns] AS [Extent4]
WHERE ([Extent4].[Day] >= '2017-09-01') AND ([Extent4].[Day] <= '2017-09-30') AND (([Project5].[C2] = (SUBSTRING([Extent4].[SYSU], 0 + 1, 2))) OR (([Project5].[C2] IS NULL) AND (SUBSTRING([Extent4].[SYSU], 0 + 1, 2) IS NULL)))) AS [C2]
FROM ( SELECT
[GroupBy3].[A1] AS [C1],
[GroupBy3].[K1] AS [C2]
FROM ( SELECT
[Filter3].[K1] AS [K1],
SUM([Filter3].[A1]) AS [A1]
FROM ( SELECT
SUBSTRING([Extent3].[SYSU], 0 + 1, 2) AS [K1],
[Extent3].[NbrOfJobRunsSucceeded] AS [A1]
FROM [dbo].[DollarU_JobRuns] AS [Extent3]
WHERE ([Extent3].[Day] >= '2017-09-01') AND ([Extent3].[Day] <= '2017-09-30')
) AS [Filter3]
GROUP BY [K1]
) AS [GroupBy3]
) AS [Project5]
) AS [Project6]
) AS [Project7]
ORDER BY [Project7].[C2] DESC
OFFSET 10 ROWS ) AS [UnionAll1]
GROUP BY [UnionAll1].[C1]
) AS [GroupBy5]
) AS [Project9]
ORDER BY [Project9].[C3] DESC
我还创建了一个SQL视图，它为我提供了相同的结果：
With TopItems As
(
SELECT SUBSTRING( [SYSU],1,2) AS [System]
, Sum([NbrOfJobRunsSucceeded]) AS NbrOfJobRunsSucceeded
, Sum([NbrOfJobRunsFailed]) AS NbrOfJobRunsFailed
, Sum([NbrOfJobRunsSucceeded] + [NbrOfJobRunsFailed]) AS Total
, ROW_NUMBER() OVER (ORDER BY Sum([NbrOfJobRunsSucceeded] + [NbrOfJobRunsFailed]) DESC) AS Num
FROM [dbo].[DollarU_JobRuns]
WHERE [Day] >= DATEADD(month, -1, DATEADD(month, DATEDIFF(month, 0, GETDATE()), 0))
AND [Day] < DATEADD(month, DATEDIFF(month, 0, GETDATE()), 0)
GROUP BY SUBSTRING( [SYSU],1,2)
)
SELECT [System], NbrOfJobRunsSucceeded, NbrOfJobRunsFailed, Total
FROM TopItems
WHERE Num <= 10
UNION ALL
SELECT
'Others'
, Sum([NbrOfJobRunsSucceeded]) AS NbrOfJobRunsSucceeded
, Sum([NbrOfJobRunsFailed]) AS NbrOfJobRunsFailed
, Sum(Total)
FROM TopItems
WHERE Num > 10
首先比较结果时，我发现我自己精心制作的SQL视图更简洁。但是我喜欢创建 LINQ 语句，它也非常简洁，但生成的 SQL 查询非常大且无法理解。但是无论产生什么（无论如何都在引擎盖下）只要性能正常就没有那么重要。但 SQL 视图的执行时间为 27.5 毫秒，比 LINQ 生成的查询的 120.3 毫秒快得多。
LINQ 使用起来很糟糕，还是我错过了一些东西来提高它的性能？
看起来使用组聚合的 2 个let语句的 EF 查询翻译存在缺陷。您可以尝试改用多重投影：
var baseQuery = DollarU_JobRuns
.Where(jr => jr.Day >= first && jr.Day <= last)
.GroupBy(jr => new { System = jr.SYSU.Substring(0, 2) })
.Select(systemGroup => new
{
System = systemGroup.Key.System,
NbrOfJobRunsSucceeded = systemGroup.Sum(x => x.NbrOfJobRunsSucceeded),
NbrOfJobRunsFailed = systemGroup.Sum(x => x.NbrOfJobRunsFailed),
})
.Select(item => new
{
item.System,
item.NbrOfJobRunsSucceeded,
item.NbrOfJobRunsFailed,
Total = item.NbrOfJobRunsFailed + item.NbrOfJobRunsFailed
})
.OrderByDescending(item => item.Total);
因此，最终查询现在转换为：
SELECT
[Project5].[C5] AS [C1],
[Project5].[C4] AS [C2],
[Project5].[C1] AS [C3],
[Project5].[C2] AS [C4],
[Project5].[C3] AS [C5]
FROM ( SELECT
[GroupBy3].[A1] AS [C1],
[GroupBy3].[A2] AS [C2],
[GroupBy3].[A3] AS [C3],
[GroupBy3].[K1] AS [C4],
1 AS [C5]
FROM ( SELECT
[UnionAll1].[C1] AS [K1],
SUM([UnionAll1].[C2]) AS [A1],
SUM([UnionAll1].[C3]) AS [A2],
SUM([UnionAll1].[C4]) AS [A3]
FROM (SELECT TOP (10)
[Project1].[C3] AS [C1],
[Project1].[C1] AS [C2],
[Project1].[C2] AS [C3],
[Project1].[C4] AS [C4]
FROM ( SELECT
[GroupBy1].[A1] AS [C1],
[GroupBy1].[A2] AS [C2],
[GroupBy1].[K1] AS [C3],
[GroupBy1].[A2] + [GroupBy1].[A2] AS [C4]
FROM ( SELECT
[Filter1].[K1] AS [K1],
SUM([Filter1].[A1]) AS [A1],
SUM([Filter1].[A2]) AS [A2]
FROM ( SELECT
SUBSTRING([Extent1].[SYSU], 0 + 1, 2) AS [K1],
[Extent1].[NbrOfJobRunsSucceeded] AS [A1],
[Extent1].[NbrOfJobRunsFailed] AS [A2]
FROM [dbo].[DollarU_JobRuns] AS [Extent1]
WHERE ([Extent1].[Day] >= @p__linq__0) AND ([Extent1].[Day] <= @p__linq__1)
) AS [Filter1]
GROUP BY [K1]
) AS [GroupBy1]
) AS [Project1]
ORDER BY [Project1].[C4] DESC
UNION ALL
SELECT
[Project3].[C4] AS [C1],
[Project3].[C1] AS [C2],
[Project3].[C2] AS [C3],
[Project3].[C5] AS [C4]
FROM ( SELECT
[GroupBy2].[A1] AS [C1],
[GroupBy2].[A2] AS [C2],
[GroupBy2].[A2] + [GroupBy2].[A2] AS [C3],
N'Others' AS [C4],
[GroupBy2].[A1] + [GroupBy2].[A2] AS [C5]
FROM ( SELECT
[Filter2].[K1] AS [K1],
SUM([Filter2].[A1]) AS [A1],
SUM([Filter2].[A2]) AS [A2]
FROM ( SELECT
SUBSTRING([Extent2].[SYSU], 0 + 1, 2) AS [K1],
[Extent2].[NbrOfJobRunsSucceeded] AS [A1],
[Extent2].[NbrOfJobRunsFailed] AS [A2]
FROM [dbo].[DollarU_JobRuns] AS [Extent2]
WHERE ([Extent2].[Day] >= @p__linq__2) AND ([Extent2].[Day] <= @p__linq__3)
) AS [Filter2]
GROUP BY [K1]
) AS [GroupBy2]
) AS [Project3]
ORDER BY [Project3].[C3] DESC
OFFSET 10 ROWS ) AS [UnionAll1]
GROUP BY [UnionAll1].[C1]
) AS [GroupBy3]
) AS [Project5]
ORDER BY [Project5].[C3] DESC
我
建议您创建一个更接近业务域的视图，并考虑在 EF 模型中引用该视图。