请帮我解决这个查询（sql server 2008）

ALTER PROCEDURE ReadNews

 @CategoryID INT,
 @Culture TINYINT = NULL,
 @StartDate DATETIME = NULL,
 @EndDate DATETIME = NULL,
 @Start BIGINT, -- for paging
 @Count BIGINT -- for paging

AS
BEGIN
  SET NOCOUNT ON;  

  --ItemType for news is 0
  ;WITH Paging AS
  (
   SELECT news.ID,
     news.Title,
     news.Description,
     news.Date,
     news.Url,
     news.Vote,
     news.ResourceTitle,
     news.UserID,

     ROW_NUMBER() OVER(ORDER BY news.rank DESC) AS RowNumber, TotalCount = COUNT(*) OVER()

   FROM dbo.News news
   JOIN ItemCategory itemCat ON itemCat.ItemID = news.ID
   WHERE itemCat.ItemType = 0 -- news item 
     AND itemCat.CategoryID = @CategoryID
     AND (
       (@StartDate IS NULL OR news.Date >= @StartDate) AND 
       (@EndDate IS NULL OR news.Date <= @EndDate)
      )
     AND news.Culture = @Culture
     and news.[status] = 1

  )  
  SELECT * FROM Paging WHERE RowNumber >= @Start AND RowNumber <= (@Start + @Count - 1)
  OPTION (OPTIMIZE FOR (@CategoryID  UNKNOWN, @Culture UNKNOWN))
END  

这是结构News and ItemCategory tables:

CREATE TABLE [dbo].[News](
 [ID] [bigint] NOT NULL,
 [Url] [varchar](300) NULL,
 [Title] [nvarchar](300) NULL,
 [Description] [nvarchar](3000) NULL,
 [Date] [datetime] NULL,
 [Rank] [smallint] NULL,
 [Vote] [smallint] NULL,
 [Culture] [tinyint] NULL,
 [ResourceTitle] [nvarchar](200) NULL,
 [Status] [tinyint] NULL

 CONSTRAINT [PK_News] PRIMARY KEY CLUSTERED 
(
 [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE TABLE [ItemCategory](
 [ID] [bigint] IDENTITY(1,1) NOT NULL,
 [ItemID] [bigint] NOT NULL,
 [ItemType] [tinyint] NOT NULL,
 [CategoryID] [int] NOT NULL,
 CONSTRAINT [PK_ItemCategory] PRIMARY KEY CLUSTERED 
(
 [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

此查询读取特定类别的新闻（体育、政治……）。@Culture参数指定新闻的语言，如0（英语）、1（法语）等。ItemCategory表将新闻记录与一个或多个类别相关联。ItemType列于ItemCategory表指定了哪种类型itemID有没有。目前，我们只有ItemType0 表示ItemID引用一条记录News table.

目前，我有以下索引ItemCategory table:

CREATE NONCLUSTERED INDEX [IX_ItemCategory_ItemType_CategoryID__ItemID] ON [ItemCategory] 
(
 [ItemType] ASC,
 [CategoryID] ASC
)
INCLUDE ( [ItemID])

以及新闻表的以下索引（由查询分析器建议）：

CREATE NONCLUSTERED INDEX [_dta_index_News_8_1734000549__K1_K7_K13_K15] ON [dbo].[News] 
(
 [ID] ASC,
 [Date] ASC,
 [Culture] ASC,
 [Status] ASC
)

使用这些索引，当我执行查询时，对于某些参数，查询执行时间不到一秒，而对于其他参数（例如不同的@Culture或@CategoryID）可能最多需要2分钟！我用过OPTIMIZE FOR (@CategoryID UNKNOWN, @Culture UNKNOWN)防止参数嗅探@CategoryID and @Culture参数，但似乎不适用于某些参数。

目前大约有 2,870,000 条记录News表和 4,740,000ItemCategory table.

现在，我非常感谢有关如何优化此查询或其索引的任何建议。

update: execution plan:

(in this image, ItemNetwork is what I referred to as ItemCategory. they are the same)

您是否看过一些内置的 SQL 工具来帮助您解决此问题：

IE。从管理工作室菜单：

• '查询'->'显示估计执行计划'
• '查询'->'包括实际执行计划'
• “工具”->“数据库引擎优化顾问”