第4章创建商品目录

演示了新表的创建，主键的创建，外部关键字的约束，利用数据库关系图来显示和管理外键的约束，实现多对多的关系。

利用存储过程在数据层实现分页，这是性能最高的一种分页方式，原理如下：

在SQL2005中支持对结果集的行进行编号，这样我们要取出结果中6到10条的记录就可以这样写：

--申明临时表变量@Products
declare @Products TABLE
(RowID int,
ProductID int,
Name nvarchar(50),
Description nvarchar(1000))

--向临时表赋值
insert into @Products
select row_number() over (order by productid) as rowid, productid,name,description from product

--从临时表中取数据
select productid,Name,Description FROM @Products
where rowid>=6 and rowid<=10

实际应用在获取分类中商品的存储过程代码如下：

create procedure GetProductInCategory
(@CategoryID INT,
@DescriptionLength INT,
@PageNumber INT,
@ProductsPerPage INT,
@HowManyProducts INT OUTPUT)
AS

DECLARE @Products TABLE
(RowID INT,
ProductID INT,
Name NVARCHAR(50),
Description NVARCHAR(1000),
Price Money,
Img1File NVARCHAR(50),
Img2File NVARCHAR(50),
OnSub1Promotion bit,
OnCatalogPromotion bit
)

INSERT INTO @Products
SELECT ROW_NUMBER() OVER (ORDER BY Product.ProductID),Product.ProductID,Name,SUBSTRING(Description,1,@DescriptionLength) +'

' AS Description,
Price,Img1File,Img2File,OnSub1Promotion,OnCatalogPromotion FROM Product INNER JOIN ProductCategory
ON Product.ProductID=ProductCategory.ProductID
WHERE ProductCategory.CategoryID=@CategoryID

SELECT @HowManyProducts = COUNT(ProductID) FROM @Products

SELECT ProductID,Name,Description,Price,Img1File,Img2File,OnSub1Promotion,OnCatalogPromotion
FROM @products
WHERE RowID>(@PageNumber-1)*@ProductsPerPage AND RowID<=@PageNumber*@ProductsPerPage

获取某个大类下推荐的商品列表的存储过程GetProductOnSub1Promotion：

create procedure GetProductOnSub1Promotion
(@Sub1ID INT,
@DescriptionLength INT,
@PageNumber INT,
@ProductsPerPage INT,
@HowManyProducts INT OUTPUT)
AS

DECLARE @Products TABLE
(RowID INT,
ProductID INT,
Name NVARCHAR(50),
Description NVARCHAR(1000),
Price Money,
Img1File NVARCHAR(50),
Img2File NVARCHAR(50),
OnSub1Promotion bit,
OnCatalogPromotion bit
)

INSERT INTO @Products
SELECT ROW_NUMBER() OVER (ORDER BY ProductID) AS Row,ProductID,Name,SUBSTRING(Description,1,@DescriptionLength) +'

' AS Description,
Price,Img1File,Img2File,OnSub1Promotion,OnCatalogPromotion FROM
(SELECT DISTINCT Product.ProductID,Product.Name,SUBSTRING(Product.Description,1,@DescriptionLength)+'

' AS Description,Price,Img1File,Img2File,OnSub1Promotion,OnCatalogPromotion
FROM Product INNER JOIN ProductCategory ON Product.ProductID=ProductCategory.ProductID
INNER JOIN Category ON ProductCategory.CategoryID=Category.CategoryID
WHERE Product.OnSub1Promotion=1
AND Category.Sub1ID=@Sub1ID)
AS ProductOnSub1Pr

SELECT @HowManyProducts = COUNT(ProductID) FROM @Products

SELECT ProductID,Name,Description,Price,Img1File,Img2File,OnSub1Promotion,OnCatalogPromotion
FROM @products
WHERE RowID>(@PageNumber-1)*@ProductsPerPage AND RowID<=@PageNumber*@ProductsPerPage

嗯这样的支持分页的存储过程代码性能很不错不过只有SQL2005支持。接下来是业务层的编码，其功能呢个只是调用数据层的存储过程。里面提到了使用结构类型，他是一个值类型，比引用类型如类效率要高。

表示层主要是编写用户控件，这里要注意的是，控件里如果是用的ASP.NET语法，则需要使用相对路径，因为控件是存放在/UserControls子目录下的，如

<asp:HyperLink ID="HyperLink1" Runat="server" NavigateUrl='<%# "../Catalog.aspx?Sub1ID="+Request.QueryString["Sub1ID"]+"&CategoryID=" + Eval("CategoryID") %>'

但如果是使用HTML语法，就不需要使用相对路径了，可以理解为是类似于shtml方式的嵌入，比如：

<asp:DataList ID="list" Runat="server" RepeatColumns="2">
<ItemTemplate>
<a class="ProductName" href='Product.aspx?ProductID=<%# Eval("ProductID")%> '><%# Eval("Name") %></a>

在表示层中最大的挑战是实现翻页链接，为了获取URL中QueryString的参数并且再加上page页码的参数组合成新的url查询参数，程序引用了

using System.Collections.Specialized;

对前一页PreLink和NextLink的链接赋值如下：

        if (howManyPages > 1)
        {
            int currPage = Int32.Parse(page);
            pagingLabel.Visible = true;
            preLink.Visible = true;
            nextLink.Visible = true;
            pagingLabel.Text = "第" + page + "页，共" + howManyPages.ToString() + "页";
            if (currPage == 1)
                preLink.Enabled = false;
            else
            {
                NameValueCollection query = Request.QueryString;
                string paramName, newQueryString = "?";
                for (int i = 0; i < query.Count; i++)
                    if (query.AllKeys[i] != null)
                        if ((paramName = query.AllKeys[i].ToString()).ToUpper() != "PAGE")
                            newQueryString += paramName + "=" + query[i] + "&";
                preLink.NavigateUrl = Request.Url.AbsolutePath + newQueryString + "Page=" + (currPage - 1).ToString();
            }

            if (currPage == howManyPages)
                nextLink.Enabled = false;
            else
            {
                NameValueCollection query = Request.QueryString;
                string paramName, newQueryString = "?";
                for (int i = 0; i < query.Count; i++)
                    if (query.AllKeys[i] != null)
                        if ((paramName = query.AllKeys[i].ToString()).ToUpper() != "PAGE")
                            newQueryString += paramName + "=" + query[i] + "&";
                nextLink.NavigateUrl = Request.Url.AbsolutePath + newQueryString + "Page=" + (currPage + 1).ToString();
            }
        }

第4章 创建商品目录

第4章创建商品目录