对于NVARCHAR（最大），我只得到4000个字符的TSQL？(For Nvarchar(Max)

这是2005年SS。

为什么我我只得到4000个字符，而不是8000？

它截断在4000字符串@ SQL1。

ALTER PROCEDURE sp_AlloctionReport(
    @where NVARCHAR(1000),
    @alldate NVARCHAR(200),
    @alldateprevweek NVARCHAR(200))
AS
    DECLARE @SQL1 NVARCHAR(Max)

    SET @SQL1 = 'SELECT DISTINCT VenueInfo.VenueID, VenueInfo.VenueName, VenuePanels.PanelID, 
    VenueInfo.CompanyName, VenuePanels.ProductCode, VenuePanels.MF, VenueInfo.Address1, 
    VenueInfo.Address2, '' As AllocationDate, '' As AbbreviationCode, VenueInfo.Suburb, VenueInfo.Route, VenueInfo.ContactFirstName, 
    VenueInfo.ContactLastName, VenueInfo.SuitableTime, VenueInfo.OldVenueName, 
    VenueCategories.Category, VenueInfo.Phone, VenuePanels.Location, VenuePanels.Comment, 
    [VenueCategories].[Category] + '' Allocations'' AS ReportHeader, 
    ljs.AbbreviationCode AS PrevWeekCampaign
    FROM (((VenueInfo INNER JOIN VenuePanels ON VenueInfo.VenueID = VenuePanels.VenueID) 
    INNER JOIN VenueCategories ON VenueInfo.CategoryID = VenueCategories.CategoryID) 
    LEFT JOIN (SELECT CampaignProductions.AbbreviationCode, VenuePanels.PanelID, CampaignAllocations.AllocationDate
                    FROM (((VenueInfo INNER JOIN VenuePanels ON VenueInfo.VenueID=VenuePanels.VenueID) INNER JOIN CampaignAllocations ON VenuePanels.PanelID=CampaignAllocations.PanelID) INNER JOIN CampaignProductions ON CampaignAllocations.CampaignID=CampaignProductions.CampaignID) INNER JOIN VenueCategories ON VenueInfo.CategoryID=VenueCategories.CategoryID
                    WHERE ' + @alldateprevweek + ') ljs
                ON VenuePanels.PanelID = ljs.PanelID) 
    INNER JOIN (SELECT VenueInfo.VenueID, VenuePanels.PanelID, VenueInfo.VenueName, VenueInfo.CompanyName, VenuePanels.ProductCode, 
                VenuePanels.MF, VenueInfo.Address1, VenueInfo.Address2, CampaignAllocations.AllocationDate, 
                CampaignProductions.AbbreviationCode, VenueInfo.Suburb, VenueInfo.Route, VenueInfo.ContactFirstName, 
                VenueInfo.ContactLastName, VenueInfo.SuitableTime, VenueInfo.OldVenueName, VenueCategories.Category, 
                VenueInfo.Phone, VenuePanels.Location, VenuePanels.Comment, [Category] + '' Allocations'' AS ReportHeader, 
                ljs2.AbbreviationCode AS PrevWeekCampaign
                FROM ((((VenueInfo INNER JOIN VenuePanels ON VenueInfo.VenueID = VenuePanels.VenueID) 
                INNER JOIN CampaignAllocations ON VenuePanels.PanelID = CampaignAllocations.PanelID) 
                INNER JOIN CampaignProductions ON CampaignAllocations.CampaignID = CampaignProductions.CampaignID) 
                INNER JOIN VenueCategories ON VenueInfo.CategoryID = VenueCategories.CategoryID) 
                LEFT JOIN (SELECT CampaignProductions.AbbreviationCode, VenuePanels.PanelID, CampaignAllocations.AllocationDate
                                FROM (((VenueInfo INNER JOIN VenuePanels ON VenueInfo.VenueID=VenuePanels.VenueID) INNER JOIN CampaignAllocations ON VenuePanels.PanelID=CampaignAllocations.PanelID) INNER JOIN CampaignProductions ON CampaignAllocations.CampaignID=CampaignProductions.CampaignID) INNER JOIN VenueCategories ON VenueInfo.CategoryID=VenueCategories.CategoryID
                                WHERE ' + @alldateprevweek + ') ljs2
                            ON VenuePanels.PanelID = ljs2.PanelID
                WHERE ' + @alldate + ' AND ' + @where + ') ljs3
                ON VenueInfo.VenueID = ljs3.VenueID
    WHERE (((VenuePanels.PanelID)<>ljs3.[PanelID] And 
        (VenuePanels.PanelID) Not In (SELECT PanelID FROM CampaignAllocations WHERE ' + @alldateprevweek + ')) 
        AND ' + @where + ')
    UNION ALL
     SELECT VenueInfo.VenueID, VenueInfo.VenueName, VenuePanels.PanelID, VenueInfo.CompanyName, VenuePanels.ProductCode, 
    VenuePanels.MF, VenueInfo.Address1, VenueInfo.Address2, CampaignAllocations.AllocationDate, 
    CampaignProductions.AbbreviationCode, VenueInfo.Suburb, VenueInfo.Route, VenueInfo.ContactFirstName, 
    VenueInfo.ContactLastName, VenueInfo.SuitableTime, VenueInfo.OldVenueName, VenueCategories.Category, 
    VenueInfo.Phone, VenuePanels.Location, VenuePanels.Comment, [Category] + '' Allocations'' AS ReportHeader, 
    ljs.AbbreviationCode AS PrevWeekCampaign
    FROM ((((VenueInfo INNER JOIN VenuePanels ON VenueInfo.VenueID = VenuePanels.VenueID) 
    INNER JOIN CampaignAllocations ON VenuePanels.PanelID = CampaignAllocations.PanelID) 
    INNER JOIN CampaignProductions ON CampaignAllocations.CampaignID = CampaignProductions.CampaignID) 
    INNER JOIN VenueCategories ON VenueInfo.CategoryID = VenueCategories.CategoryID) 
    LEFT JOIN (SELECT CampaignProductions.AbbreviationCode, VenuePanels.PanelID, CampaignAllocations.AllocationDate
                    FROM (((VenueInfo INNER JOIN VenuePanels ON VenueInfo.VenueID=VenuePanels.VenueID) INNER JOIN CampaignAllocations ON VenuePanels.PanelID=CampaignAllocations.PanelID) INNER JOIN CampaignProductions ON CampaignAllocations.CampaignID=CampaignProductions.CampaignID) INNER JOIN VenueCategories ON VenueInfo.CategoryID=VenueCategories.CategoryID
                    WHERE ' + @alldateprevweek + ') ljs
                ON VenuePanels.PanelID = ljs.PanelID
    WHERE ' + @alldate + ' AND ' + @where

    Select @SQL1

Answer 1:

您已经声明此为为nvarchar（最大），它允许2GB的数据，因此将存储2GB。

怎么了：

数据类型还没有为nvarchar（最大），直到分配给@ SQL1
在此之前，它是字符串的集合，每件不超过4000（常量）
您正在连接具有短变量短常数（短= <4000）
所以，你有4000个字符的投入@ SQL1

所以，你必须确保你有在右手边为nvarchar（最大）。

一个想法。所述第二线串接以恒定= nvarchar的（最大）为nvarchar（最大）

SET @SQL1 = ''
SET @SQL1 = @SQL1 + 'SELECT DISTINCT Venue...
   ....

这是该整数除法是发生在每一个的langauge没有什么不同。

declare @myvar float
set @myvar = 1/2 --gives zero because it's integer on the right

运算符优先级（推断类型优先级）始终是“转让”最后......为什么要统一在SQL Server中的字符串有什么不同？

Answer 2:

更新： GBN的答案是正确的，我错了。正如MSDN指出的，为nvarchar（最大）支持高达2 ^ 31-1个字节的数据，存储为UCS-2的（每字符的2字节，加上2 BOM）。你的问题似乎是与字符串连接，而不是数据类型的限制。

这就是说，如果你用它来建立一个SQL字符串，为什么不使用VARCHAR？你有没有在数据库的本地字符集（通常的Latin-1）表示的字段名？

最后 - 你可以在你的存储过程只是不使用动态SQL简化整个问题。创建一个把你的where子句的字符串，返回的表，然后就加入他们在你的程序中的一些表值函数。作为奖励它几乎肯定会快很多，因为在最起码的数据库将能够缓存SP身体作为一个准备好的声明。

Answer 3:

我解决问题，只是举出N字每个字符串和问题解决了，例如前

declare @sql nvarchar(max) = '' + @Where + 'SomeThing';

一定是

declare @sql nvarchar(max) = N'' + @Where + N'SomeThing';

如果设置字符串为空还必须设置N“”

if @where is null
set @where = N''

:-)简单的答案