帮忙看看这一段存储过程的代码，老是报错。解决方案

帮忙看看这一段存储过程的代码，老是报错。
ELSE   IF(@topnum> 0)
        BEGIN
        IF(@type> 0)

        SELECT   TOP   (@topnum)
        A.ArticleID,
        A.ArticleTitle,
        A.ArticleContent,
        A.ArticleImg,
        PublicDate,
        ViewTimes,
        A.ArticleType   As   TypeID,
        B.TypeTxt
        FROM     ArticleInfo   A
        JOIN     TypeInfo   B
        ON   A.ArticleType=B.TypeID
        AND   [email protected]
        ORDER   BY   ArticleID   DESC
END
  Incorrect   syntax   near   '( '.SELECT   TOP   (@topnum)指的是这一行

------解决方案--------------------
TOP后只允许使用常数，不能使用变量。

可以使用动态SQL或SET ROWCOUNT
------解决方案--------------------
delcare @sql varchar(300)
set @sql= 'SELECT TOP '+ (@topnum)+ '
A.ArticleID,
A.ArticleTitle,
A.ArticleContent,
A.ArticleImg,
PublicDate,
ViewTimes,
A.ArticleType As TypeID,
B.TypeTxt
FROM ArticleInfo A
JOIN TypeInfo B
ON A.ArticleType=B.TypeID
AND [email protected]
ORDER BY ArticleID DESC '

exec (@sql)
------解决方案--------------------
ELSE IF(@topnum> 0)
BEGIN
IF(@type> 0)

exec( 'SELECT TOP '[email protected]+ ' A.ArticleID,A.ArticleTitle,A.ArticleContent,A.ArticleImg,PublicDate,ViewTimes,A.ArticleType As TypeID,B.TypeTxt FROM ArticleInfo A JOIN TypeInfo B ON A.ArticleType=B.TypeID AND A.ArticleType= '[email protected]+ ' ORDER BY ArticleID DESC ')
END