SELECT TOP（N）每個組的行

Question

這是我到目前為止的查詢：

SELECT [Id], [HotelName], [StarRating], [Description], [CheckinDate], [CheckoutDate], [Price], [ImageUrl]
FROM
(
    SELECT TOP (6) [Id], [HotelName], [StarRating], [Description], [CheckinDate], [CheckoutDate], [Price], [ImageUrl], RANK() OVER(PARTITION BY [StarRating] ORDER BY [StarRating]) AS Num
    FROM [dbo].[Hotel]
    WHERE [CityId] = @CityId 
    AND CheckinDate > GETDATE()
    AND [StarRating] IN (3, 4, 5)
) X
WHERE Num <= 2

我想要的是為每個星級評分獲得2行：評級3中的2，評級4中的2和評級5中的2。我該怎么做？ 我已經在網上進行了一些研究后得出了上述內容，但我顯然還沒有完全理解hwo來實現它，因為它不起作用...我得到了6行星級3

Answer 1

使用ROW_NUMBER函數 - 例如，

WITH X 
AS
(
    SELECT 
       [Id], [HotelName], [StarRating], [Description], 
       [CheckinDate], [CheckoutDate], [Price], [ImageUrl], 
       ROW_NUMBER() OVER(PARTITION BY [StarRating] ORDER BY [Id]) AS Num
    FROM 
       [dbo].[Hotel]
    WHERE 
       [CityId] = @CityId 
         AND CheckinDate > GETDATE()
         AND [StarRating] IN (3, 4, 5)
) 
SELECT 
   [Id], [HotelName], [StarRating], [Description], 
   [CheckinDate], [CheckoutDate], [Price], [ImageUrl]
FROM 
   X
WHERE 
   Num <= 2