T-SQL SELECT頂部按LastUpdateDateTime分類

Question

我想要一個更優雅的方式，通過LastUpdatedDateTime降序選擇下表中的頂級類別。基本上我只想查看CategoryID的每個Category的最新單行。

我可以通過執行以下操作...

SELECT Category, 
    MAX(LastUpdateDateTime) as LastUpdateDateTime 
INTO #t 
FROM Settings 
WHERE CatalogID = 123 
GROUP BY Category 
ORDER BY Category 

SELECT s.* 
FROM Settings s 
INNER JOIN #t t 
ON s.Category = t.Category 
AND s.LastUpdateDateTime = t.LastUpdateDateTime 

- >設置表

CREATE TABLE [dbo].[Settings](
[ID] [int] IDENTITY(1,1) NOT NULL, 
[CatalogID] [int] NOT NULL, 
[Category] [varchar](50) NOT NULL, 
[Facings] [bit] NOT NULL, 
[Quantity] [bit] NOT NULL, 
[LastUpdateDateTime] [datetime] NOT NULL, 
CONSTRAINT [PK_Settings_1] PRIMARY KEY CLUSTERED 
(
[ID] ASC, 
[CatalogID] ASC, 
[Category] ASC 
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,  ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] 
) ON [PRIMARY] 

這很簡單，只要找人點我在正確的方向更有效地做到這一點。我有什麼工作。我想要重構。

感謝您的期待。

-B

Answer 1

怎麼樣一個子查詢：

select s1.* 
from settings s1 
inner join 
(
    select category, max(LastUpdateDateTime) as LastUpdateDateTime 
    from settings 
    where catalogid = 123 
    group by category 
) s2 
    on s1.category = s2.category 
    and s1.LastUpdateDateTime = s2.LastUpdateDateTime 

甚至使用CTE：

;with cte as 
(
    select *, 
    row_number() over(partition by catalogid 
         order by LastUpdateDateTime desc) rn 
    from settings 
    where catalogid = 123 
) 
select * 
from cte 
where rn = 1