如何为sql server 2012中的另一个表中的每个父主键选择一个表的给定行数？

I have two tables in sql. One is a table of test cases and the other is a table of test runs with a foreign key that links back to a test case. I want to get the most recent 10 test runs for each test case. I don't want to loop through if I don't have to, but I don't see any other way to solve this problem. What is the most effective way to handle this sort of thing in sql server?

我在sql中有两个表。一个是测试用例表，另一个是测试运行表，其中一个外键链接回测试用例。我想为每个测试用例获得最近10次测试运行。如果我不需要，我不想循环，但我没有看到任何其他方法来解决这个问题。在sql server中处理这类事情最有效的方法是什么？

3 个解决方案

#1

The idea:

想法：

select
    ...
from <test cases> as tc
    outer apply (
        select top 10 *
        from <test runs> as tr
        where
            tr.<test case id> = tc.<id>
        order by tr.<date time> desc
    ) as tr

or, if you just need to get data from table:

或者，如果您只需要从表中获取数据：

;with cte_test_runs as (
   select
        *,
        row-Number() over(partition by <test case id> order by <date time> desc) as rn
    from <test runs>
)
select *
from cte_test_runs
where rn <= 10

#2

You can use Row No. Use Inner of Left Join as the case may be..

您可以根据具体情况使用行号使用左内连接。

Select * from testCase a 
left outer join 
(Select Row_number() over (partition by testcase order by RecentDate desc ) RowNo, *  from TestRuns) b
on a.pk = b.fk
where b.RowNo <=10

#3

You could use CROSS APPLY to select the top 10 per testCase ordered by date (or anyother ordering criteria).

您可以使用CROSS APPLY选择按日期排序的每个testCase的前10个（或任何其他订购标准）。

See the related question 'When should I use Cross Apply over Inner Join?' which explains it better than I can. https://*.com/a/1139231/1620715

请参阅相关问题“我应该何时使用Cross Apply over Inner Join？”这比我能解释得更好。 https://*.com/a/1139231/1620715

In your case:

在你的情况下：

SELECT * from TestCase T
CROSS APPLY 
( SELECT TOP 10 * from TestRuns R where T.TestCaseId = R.TestCaseId
 order by R.TestDate desc) TopResults

#1