EF。如何联合表格,排序行和获取顶级实体? [英] EF. How to union tables, sort rows, and get top entities?
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问题描述
T1
--------
Id,Timestamp,Text1
T2
--------
Id,时间戳,Text2
使用SQL可以这样做:
SELECT TOP 10 * FROM
(
SELECT
[Timestamp],
[Text1]
FROM
T1
UNION
SELECT
[Timestamp],
[Text2]
FROM
T2
)as x
ORDER BY [Timestamp]
问:如何使用EF linq执行该任务?
解决方案
您需要具有相同属性名称和类型的匿名类型,才能执行 Union
操作:
var t1List = from all in all $ $ $ $ $ $ $ $ $ $ $ b TimeStamp = a.TimeStamp,
Text = a.Text1
};
var t2List = from b in allT2
选择新
{
TimeStamp = b.TimeStamp,
Text = b.Text2
};
var result = t1List.Union(t2List).OrderBy(ab => ab.TimeStamp).Take(10);
I want to union records from 2 tables, sort them, and read TOP rows from result set.
T1
--------
Id, Timestamp, Text1
T2
--------
Id, Timestamp, Text2
With SQL it can be done this way:
SELECT TOP 10 * FROM
(
SELECT
[Timestamp],
[Text1]
FROM
T1
UNION
SELECT
[Timestamp],
[Text2]
FROM
T2
) as x
ORDER BY [Timestamp]
Q: How can I do that task using EF linq?
解决方案
You need an anonymous type with the same property names and types before you can do an Union
operation:
var t1List = from a in allT1
select new
{
TimeStamp = a.TimeStamp,
Text = a.Text1
};
var t2List = from b in allT2
select new
{
TimeStamp = b.TimeStamp,
Text = b.Text2
};
var result = t1List.Union(t2List).OrderBy(ab => ab.TimeStamp).Take(10);
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