极限记录

Question

我有这个功能从数据库中显示记录到FlowLayoutPanel的

flowLayoutPanel1.Controls.Clear(); 
     using (SqlConnection myDatabaseConnection = new SqlConnection(myConnectionString.ConnectionString)) 
     { 
      myDatabaseConnection.Open(); 
      string a = "Select EmpID, Name from EmpTable"; 
      using (SqlCommand SqlCommand = new SqlCommand(" "+ a +" ", myDatabaseConnection)) 
      { 
       int i = 0; 
       SqlDataReader DR1 = SqlCommand.ExecuteReader(); 
       while (DR1.Read()) 
       { 
        i++; 
        BookUserControl usercontrol = new BookUserControl(); 
        usercontrol.Tag = i; 
        usercontrol.EmpID = DR1["EmpID"].ToString(); 
        usercontrol.Name = (string)DR1["Name"]; 
        flowLayoutPanel1.Controls.Add(usercontrol); 
       } 
      } 
     } 

我如何将限制将在FlowLayoutPanel中显示的记录数？我知道有选择顶部。但是，我将如何做到这一点，例如将显示10条记录，当点击下一个按钮时，将显示接下来的10条记录，当前一个按钮点击时，将显示前10条记录。

Answer 1

在SQL Server 2008中，你可以使用Row_Number()：

Select * from  
(Select row_number() over (order by EmpID) r, EmpID, Name from EmpTable) X 
where X.r between @start and @end 

供应的@start和@end的价值观和你都设置。您可能会也可能不会显示r的值。要从1-10显示，请设置@start = 1和@end = 10依此类推。在这个查询中，数据是在EmpID上订购的。

修改后的代码：

string a = "Select * from (Select row_number() over (order by EmpID) r, EmpID, Name from EmpTable) X where X.r between @start and @end"; 
     using (SqlCommand SqlCommand = new SqlCommand(" "+ a +" ", myDatabaseConnection)) 
     { 
      SqlCommand.Parameters.Add("@start").Value = 1; 
      SqlCommand.Parameters.Add("@end").Value = 10; 
      int i = 0; 
      SqlDataReader DR1 = SqlCommand.ExecuteReader(); 
      while (DR1.Read()) 
      { 
       i++; 
       BookUserControl usercontrol = new BookUserControl(); 
       usercontrol.Tag = i; 
       usercontrol.EmpID = DR1["EmpID"].ToString(); 
       usercontrol.Name = (string)DR1["Name"]; 
       flowLayoutPanel1.Controls.Add(usercontrol); 
      } 
     } 

见http://msdn.microsoft.com/en-us/library/ms186734(v=sql.90).aspx

Answer 2

是有SELECT TOP在SQL

使用这样

Select TOP(10) EmpID, Name from EmpTable 

我更新你的鳕鱼

flowLayoutPanel1.Controls.Clear(); 
     using (SqlConnection myDatabaseConnection = new SqlConnection(myConnectionString.ConnectionString)) 
     { 
      myDatabaseConnection.Open(); 
      string a = "SELECT TOP(10) EmpID, Name FROM EmpTable"; 
      using (SqlCommand SqlCommand = new SqlCommand(" "+ a +" ", myDatabaseConnection)) 
      { 
       int i = 0; 
       SqlDataReader DR1 = SqlCommand.ExecuteReader(); 
       while (DR1.Read()) 
       { 
        i++; 
        BookUserControl usercontrol = new BookUserControl(); 
        usercontrol.Tag = i; 
        usercontrol.EmpID = DR1["EmpID"].ToString(); 
        usercontrol.Name = (string)DR1["Name"]; 
        flowLayoutPanel1.Controls.Add(usercontrol); 
       } 
      } 
     } 

现在使用这个鳕鱼和这正是你想要

工作

祝你好运

Answer 3

您最优雅是使用ROW_NUMBER函数

WITH NumberedMyTable AS 
(
    SELECT 
     Id, 
     Value, 
     ROW_NUMBER() OVER (ORDER BY Id) AS RowNumber 
    FROM 
     MyTable 
) 
SELECT 
    Id, 
    Value 
FROM 
    NumberedMyTable 
WHERE 
    RowNumber BETWEEN @From AND @To 

好运