摘要： 在EXEC sp_executesql@code失败的含量比4000更长@code，但@code不截断为4000个Unicode字符。

我正在观察SQL Server 2014 Developer Edition上的问题。

更多详细信息：我的SQL安装脚本动态定义了一些代码，因为它应该修改代码以使其反映环境（在安装过程中仅一次）。让以下@datasource变量捕获特定环境的结果：

DECLARE @datasource nvarchar(100) = N'testdb.dbo.source_table'

该@code变量声明为nvarchar(max)类型，并且该REPLACE函数用于根据需要修改字符串（即用@datasource内容替换占位符）-请参见下面的代码段。

在Management Studio中执行sp_executesql时@code，将显示以下错误：

消息156，级别15，状态1，过程my_sp，第86行
关键字“ AS”附近的语法不正确。
消息102，级别15，状态1，过程my_sp，第88行
‘WHERE’附近的语法不正确。

下面的代码段是上述方法失败的精确代码副本（将被复制）。功能可能并不重要-
可能只有代码的长度是重要的。的@code内容显然是由截短sp_executesql; 但是，不应这样（请参见下文）：

-- ... repeated from above
DECLARE @datasource nvarchar(100) = N'testdb.dbo.source_table'

DECLARE @code nvarchar(MAX) = REPLACE(N'
-- Comment comment comment comment comment comment comment comment comment.
-- Comment comment comment comment comment comment comment comment comment.
-- Comment comment comment comment comment comment comment comment comment.
CREATE PROCEDURE dbo.my_sp
AS
BEGIN
    SET NOCOUNT ON
    DECLARE @result int = -555   -- Comment comment comment comment comment.

    -- Comment comment comment comment comment comment comment comment comment.
    -- Comment comment comment comment comment comment comment comment comment.
    DECLARE @info_table TABLE (
        action nvarchar(10),    -- Comment comment comment comment comment
        firmaID int,            -- Comment comment comment comment comment
        kod numeric(8, 0),      -- Comment comment comment comment comment
        oz1 nvarchar(40),       -- Comment comment comment comment comment
        oz2 nvarchar(40),       -- Comment comment comment comment comment
        oz3 nvarchar(40),
        oz4 nvarchar(40)
    )

-- Comment comment comment comment comment comment comment comment comment.
    BEGIN TRANSACTION tran_firmy
    BEGIN TRY
        MERGE dbo.firmy AS target
        USING (SELECT kod, ico, dic, nazev,
               oz1, oz2, oz3, oz4,
               jeaktivni,
               ulice, mesto, psc
               FROM @datasource) AS source
        ON target.kod = source.kod
        WHEN MATCHED AND (COALESCE(target.ico, '''') != COALESCE(source.ico, '''')
                          OR COALESCE(target.dic, '''') != COALESCE(source.dic, '''')
                          OR COALESCE(target.nazev, '''') != COALESCE(source.nazev, '''')
                          OR COALESCE(target.nepouzivat_oz1, '''') != COALESCE(source.oz1, '''')
                          OR COALESCE(target.nepouzivat_oz2, '''') != COALESCE(source.oz2, '''')
                          OR COALESCE(target.nepouzivat_oz3, '''') != COALESCE(source.oz3, '''')
                          OR COALESCE(target.nepouzivat_oz4, '''') != COALESCE(source.oz4, '''')
                          OR COALESCE(target.jeaktivni, 0) != COALESCE(source.jeaktivni, 0)
                          OR COALESCE(target.ulice, '''') != COALESCE(source.ulice, '''')
                          OR COALESCE(target.mesto, '''') != COALESCE(source.mesto, '''')
                          OR COALESCE(target.psc, '''') != COALESCE(source.psc, '''')
                          ) THEN
            UPDATE
            SET target.ico = source.ico,
                target.dic = source.dic,
                target.nazev = source.nazev,
                target.nepouzivat_oz1 = source.oz1,
                target.nepouzivat_oz2 = source.oz2,
                target.nepouzivat_oz3 = source.oz3,
                target.nepouzivat_oz4 = source.oz4,
                target.jeaktivni = source.jeaktivni,
                target.ulice = source.ulice,
                target.mesto = source.mesto,
                target.psc = source.psc,
                target.changed = GETDATE(),
                target.changedby = ''dialog''
        WHEN NOT MATCHED THEN
            INSERT (kod, ico, dic, nazev,
                    nepouzivat_oz1, nepouzivat_oz2, nepouzivat_oz3, nepouzivat_oz4,
                    jeaktivni,
                    ulice, mesto, psc,
                    created, createdby)
            VALUES (source.kod, source.ico, source.dic, source.nazev,
                    source.oz1, source.oz2, source.oz3, source.oz4,
                    source.jeaktivni,
                    source.ulice, source.mesto, source.psc,
                    GETDATE(), ''dialog'')
        OUTPUT
            $action AS action,  -- INSERT or UPDATE
            inserted.ID AS firmaID,
            inserted.kod AS kod,
            inserted.nepouzivat_oz1 AS oz1,
            inserted.nepouzivat_oz2 AS oz2,
            inserted.nepouzivat_oz3 AS oz3,
            inserted.nepouzivat_oz4 AS oz4
        INTO @info_table;

        -- Comment comment comment comment comment comment comment comment comment.
        -- Comment comment comment comment comment comment comment comment comment.
        SET @result = @@ROWCOUNT

        -- Comment comment comment comment comment comment comment comment comment.
        -- Comment comment comment comment comment comment comment comment comment.
        DELETE FROM obchodni_zastupci AS ozt
        WHERE ozt.kod IN (
            SELECT kod FROM @info_table AS it WHER it.action = ''UPDATE''
            )

        -- Comment comment comment comment comment comment comment comment comment.
        -- Comment comment comment comment comment comment comment comment comment.
        UPDATE dodaci_adresy
            SET custID = f.ID
        FROM firmy AS f,  dodaci_adresy AS da
        WHERE da.custID IS NULL AND f.kod = da.kod_firmy

        COMMIT TRANSACTION tran_firmy
    END TRY
    BEGIN CATCH
        ROLLBACK TRANSACTION tran_firmy
        SET @result = -1  -- Comment comment comment comment comment comment comment comment comment.

    END CATCH
    RETURN @result          -- Comment comment comment comment comment comment comment comment comment.
END', N'@datasource', N'testdb.dbo.source_table')


-- The following prints only show that the full-length string is there
PRINT SUBSTRING(@code, 0, 4000)
PRINT '-----------------------------------------------------------'
PRINT SUBSTRING(@code, 4000, 10000)


EXEC sp_executesql @code

-- The following command also does not work (uncomment it).
-- EXEC(@code)

-- Even splitting to two variables and passing the concatenation 
-- does not work. 
-- DECLARE @code1 nvarchar(MAX) = SUBSTRING(@code, 0, 4000)
-- DECLARE @code2 nvarchar(MAX) = SUBSTRING(@code, 4000, 10000)
-- EXEC(@code1 + @code2)

注意这两个PRINT命令。第一个打印前4000个字符，第二个打印其余的字符。它在行的中间进行了剪切，但仅用于显示@code真正包含完整的字符串。

sp_executesql（Transact-SQL）的文档说：

[@ stmt =]语句

[…]字符串的大小仅受可用的数据库服务器内存限制。在64位服务器上，字符串的大小限制为2 GB，即nvarchar（max）的最大大小。

我在其他地方找到了EXEC(@code)没有限制的使用提示sp_executesql。但是，它与文档中上面引用的部分相矛盾。而且，这EXEC(@code)也不起作用。

将替换后的相同内容复制/粘贴到SQL控制台后，它便起作用（即创建了过程）。

该如何解决？