[英]get maximum date in separated columns (month and year)
I have this table : 我有这张桌子:
Month Year Provider Number
1 2015 1 345
2 2015 1 345
3 2015 1 345
12 2015 2 444
1 2016 2 444
Let's say I want to get all different numbers by provider but only the max month and max year, something like this: 假设我想按提供商获取所有不同的数字,但只能获取最大月份和最大年份,如下所示:
Month Year Provider Number
3 2015 1 345
1 2016 2 444
I have this ugly query that I would like to improve : 我有一个我想改进的丑陋查询:
SELECT (SELECT max([Month])
FROM dbo.Info b
WHERE b.Provider = a.Provider
AND b.Number = a.Number
AND [Year] = (SELECT max([Year])
FROM dbo.Info c
WHERE c.Provider = a.Provider
AND c.Number = a.Number)) AS [Month],
(SELECT max([Year])
FROM dbo.Info d
WHERE d.Provider = a.Provider
AND d.Number = a.Number)) AS [Year],
a.Provider,
a.Number
FROM dbo.Info a
One option is to use row_number
: 一种选择是使用
row_number
:
select *
from (
select *, row_number() over (partition by provider
order by [year] desc, [month] desc) rn
from dbo.Info
) t
where rn = 1
This assumes the number and provider fields are the same. 假定数字和提供者字段相同。 If not, you may need to also partition by the number field.
如果不是,您可能还需要按数字字段进行分区。
You could use a row_number and cte 您可以使用row_number和cte
;WITH cte AS (
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY Provider ORDER BY [Year] DESC, [Month] DESC) as rNum
FROM Info)
SELECT *
FROM cte where rNum = 1
If you want to create a view then 如果要创建视图,则
CREATE VIEW SomeViewName
AS
WITH cte AS (
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY Provider ORDER BY [Year] DESC, [Month] DESC) as rNum
FROM Info)
SELECT *
FROM cte where rNum = 1
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