SqlServer性能优化 Sql语句优化（十四）

 一：在较小的结果集上上操作

    1.仅返回需要的列

    2.分页获取数据

  EF实现分页：

  public object  getcp(int skiprows,int currentpagerows)
        {          
            HRUser dbcontext = new HRUser();            
            var cps = dbcontext.Product.Join(dbcontext.ProductCategory, a => a.ProductSubcategoryKey,
                ar => ar.ProductCategoryKey, (a, ar) => new
                {
                    CName = ar.EnglishProductCategoryName,
                    PName = a.EnglishProductName,
                    Color = a.Color,
                    Size = a.Size
                });
            return cps.OrderBy(p=>p.PName).Skip(skiprows).Take(currentpagerows).ToList();
        }

 上一页：

 protected void Button4_Click(object sender, EventArgs e)
        {
            TextBox1.Text = (int.Parse(TextBox1.Text.Trim()) + 1).ToString();
            DataBinding();
        }

 下一页：

 protected void Button4_Click(object sender, EventArgs e)
        {
            TextBox1.Text = (int.Parse(TextBox1.Text.Trim()) + 1).ToString();
            DataBinding();
        }

 绑定：

 private void DataBinding()
        {
            var cps = p.getcp(int.Parse(TextBox1.Text.Trim())*10,10);
            GridView1.DataSource = cps;
            GridView1.DataBind();
        }

 避免出现左侧计算：

select * from EmployeeOp where VacationHours>=10*10
select * from EmployeeOp where VacationHours/10>=10

 建立合适的主外键：

select c.EnglishProductCategoryName,p.EnglishProductName from Product as p
inner join ProductCategory as c on c.ProductCategoryKey=p.ProductSubcategoryKey--0.214

alter table ProductCategory
add constraint pk_c_id primary key(ProductCategoryKey)

alter table Product
--不用去检查是否符合主外键的要求
with nocheck
add constraint fk_p_id foreign key(ProductSubcategoryKey) references ProductCategory(ProductCategoryKey)

select c.EnglishProductCategoryName,p.EnglishProductName from Product as p
inner join ProductCategory as c on c.ProductCategoryKey=p.ProductSubcategoryKey--性能好

 验证数据存在时使用Exists替换Count():

if ((select count(*) from EmployeeOp where VacationHours=100)>0)
print 'hello'

if exists(select * from EmployeeOp where VacationHours=100)
print 'hello1'

关闭受影响的行数：

set nocount on
select * from Product

添加稀疏列：

create table t1(c1 int identity(1,1),c2 int sparse)

declare @count int
 set @count=0
 while @count<50000
 begin
 --定义稀疏列
 insert t1 values(null)
 set @count=@count+1
 end

 --查看表空间
 sp_spaceused 't1'   --1408

 --删除稀疏列
 alter table t1
 alter column c2 drop sparse
  sp_spaceused 't1'   --1712

  --添加稀疏列
   alter table t1
 alter column c2 add sparse
   sp_spaceused 't1'  --1712

    dbcc shrinkdatabase('HRDB',1)

	--列集
	create table Student(id int,name varchar(500),sex varchar(500),sae int sparse,
	school varchar(500) sparse,optiondata xml   column_set for all_sparse_columns)

	insert Student values (1,'caojian','man','<sae>35</sae><school>cdschool</school>')
	select *from Student

	select id,name,sex,sae,school,optiondata from Student

	update Student set optiondata	='<sae>36</sae>'

	update Student set school='sunliyuan'

	create table Sales(id int identity(1,1),amount int)
	alter table Sales 
	add constraint ck_sales_amount check(amount>0)

		create table Sales1(id int identity(1,1),amount int)

		--创建规则  很多表都可以使用
			create rule amountrule as @amount>0

			--通过系统定义的方式 绑定
			exec sp_bindrule amountrule, 'Sales1.amount'

			--插入数据的时候就报错
			insert Sales1 values(0)

 

提高文件访问性能文件流：

打开SqlServer 配置管理工具：

找到如下的目录打开：

配置访问级别：

--配置访问级别  数据库级别
			sp_configure 'filestream access level',2 
			reconfigure
			select * from AdventureWorks2014.Production.Product
			select * from AdventureWorks2014.Production.ProductPhoto 
			--链接表
			select * from AdventureWorks2014.Production.ProductProductPhoto
			--存在文件系统中
			--1.创建数据库
			drop database HRSales
			create database HRSales 
			on primary
			(
			name='HRSales_data',
			filename='f:HRSales_Data.mdf'
			),
			--做文件组  --包含filestream
filegroup filestreamfilegroup contains filestream
(
name='HRSaels_Blob',
filename='f:HRSalesblob'
)
			use HRSales
			go
			create table Product(ID uniqueidentifier RowGUIDCol unique not null,
			name varchar(500),
			image varbinary(max) filestream
			)
			--插入记录
			insert into Product select NEWID(),p.Name,pp.LargePhoto from
		    AdventureWorks2014.Production.Product as p inner join
			AdventureWorks2014.Production.ProductProductPhoto as ppp on p.ProductID=ppp.ProductID inner join 
			AdventureWorks2014.Production.ProductPhoto as pp on ppp.ProductPhotoID=pp.ProductPhotoID

			select * from Product

 查看IO：

set statistics io on
select * from AdventureWorks2014.Production.ProductPhoto--io 52
set statistics io off

 

set statistics io on
select * from Product--7
set statistics io off

 

创建数据库备份设备：

--创建备份设备
sp_addumpdevice 'disk','hrsalesbak','d:hrsalesbak.bak'
--备份
backup database HRSales to hrsalesbak with name='HRSales Full',format

--恢复
restore database HRSales from hrsalesbak with file=1,recovery

文件进行了恢复：

在.Net中的显示：

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">

    <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="显示" />
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
        <Columns>
            <asp:BoundField DataField="ID" HeaderText="ID" Visible="False" />
            <asp:BoundField DataField="name" HeaderText="产品名" />
            <asp:TemplateField HeaderText="样图">
                <ItemTemplate>
                    <asp:Image ID="Image1" runat="server" ImageUrl='<%# "ImageHandler.ashx?ID="+Eval("ID") %>' />
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>

</asp:Content>

 Model层：

 SalesDbcontext dbcontext = new SalesDbcontext();
        

        public object GetAllProduct()
        {
            var allproducts = dbcontext.Product;
            return allproducts.ToList();
        }

        public byte[] GetImageByProductID(Guid id)
        {
            var product = dbcontext.Product.Where(p => p.ID == id).FirstOrDefault();
            return product.image;
        }

 后台的调用代码：

    /// <summary>
    /// ImageHandler 的摘要说明
    /// </summary>
    public class ImageHandler : IHttpHandler
    {
        Product p = new Product();
        MemoryStream memorystream = new MemoryStream();
        public void ProcessRequest(HttpContext context)
        {
            var id = Guid.Parse(context.Request.QueryString["ID"]);
            var image = p.GetImageByProductID(id);
            memorystream.Write(image, 0, image.Length);
            context.Response.Buffer = true;
            context.Response.BinaryWrite(image);
            memorystream.Dispose();
        }

      
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }