SQL ROW_NUMBER()问题与分页

Question

我使用ROW_NUMBER()函数从数据库表中获取50个50项.
@From参数是从中开始抓取50行的行.(第一次为1的是51101151等)
我传递参数@CityId到存储过程,如果第一行60中的数据库是cityId=1与cityId = 2是在排61这个存储过程不返回结果.
但是,如果我通过@From参数51而不是返回结果.我在这里做错了什么？

SELECT  RowConstrainedResult.*
FROM    ( SELECT    ROW_NUMBER() OVER 
( ORDER BY f.ItemCreatedOnDate DESC ) AS RowNum, 
f.*
FROM (
SELECT
      t.ItemIdId,
      t.ItemTypeId,
      t.CreatedOnDate as ItemCreatedOnDate,
      t.CityId as CityId
FROM   dbo.Items    as t
) f) AS RowConstrainedResult
WHERE   RowNum >= @From
    AND RowNum < @From + 50
    AND CityId = @CityId

Answer 1

在您的版本中,ROW_NUMBER()枚举所有行.将谓词移动cityid到最里面的选择,并且ROW_NUMBER()只枚举行所在的位置cityid = 2.

SELECT RowConstrainedResult.*
FROM (
     SELECT ROW_NUMBER() OVER (ORDER BY f.ItemCreatedOnDate DESC) AS RowNum, 
            f.*
     FROM (
          SELECT t.ItemIdId,
                 t.ItemTypeId,
                 t.CreatedOnDate as ItemCreatedOnDate,
                 t.CityId as CityId
          FROM dbo.Items AS t
          WHERE CityId = @CityId
          ) AS f
     ) AS RowConstrainedResult
WHERE RowNum >= @From AND 
      RowNum < @From + 50