Creating A Data Access Layer
Mar 10, 2008
Hello, everybody.
In my web application, i'm using 2 tabels; Users(Username(PK), Pwd, Name, Deptid(FK)) n Dept(Deptid(PK), Deptname)).
For creating a Data Access Layer 4 my project, I added dataset as new item n followed the wizard 2 create the required functions.
I have a function GetUser(@uname, @pwd), which takes username n password as input. M using this for authentication purpose.
While executing it poping an ConstrainException.
Plz help me out.
I've tried 2 as clear as possible here. OR u may ask me any other questions for clear picture of the scenario.
Thanks and Regards,
Sankar.
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Jun 11, 2008
I request you plz tell how to create Data Access Layer. I mean DataAccess.dll. So that I can call stored procedure from dataaccess.dll as below.
DataAccess.SqlHelper.ExecuteDataset(DataAccess.DSN.Connection("DBConnectionString"), CommandType.StoredProcedure, "SP_GetEmpIds");
I request you how can I add this stored procedures to DataAccess.dll and function. I am not having any idea in this area. I request you plz give me some suggestions to work with task.
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Nov 1, 2006
HiI'm having problems following the tutorial on creating a data access layer - http://www.asp.net/learn/dataaccess/tutorial01cs.aspx?tabid=63 - when I try to compile in Visual Studio 2005 I get namespace could not be found. I followed exactly the tutorial - I created a dataset and added this code in my aspx page. <asp:GridView ID="GridView1" runat="server" CssClass="DataWebControlStyle"> <HeaderStyle CssClass="HeaderStyle" /> <AlternatingRowStyle CssClass="AlternatingRowStyle" />In my C# file I added these lines... using NorthwindTableAdapters; <<<<<this is the problem - where does this come from? protected void Page_Load(object sender, EventArgs e) { ProductsTableAdapter productsAdapter = new ProductsTableAdapter(); GridView1.DataSource = productsAdapter.GetProducts(); GridView1.DataBind(); }Thanks in advance
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Apr 8, 2007
Before page 12, step by step instructions work!
Then there is code for AllProducts.aspx that doesn't work if one inserts the code
into the DataTutorial project started on page 1. Yes I changed the name of the CodeFile!
The code given for AllProducts.aspx.cs doesn't compile.
I was doing better without the tutorial!
I can gleen out some concepts but that is all.
If that is all, why have a tutorial?
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Oct 30, 2007
Hi guys,
I've been developing desktop client-server and web apps and have used Access and SQL Server Standard most of the time.
I'm looking into using SQL CE, and had a few questions that I can't seem to get a clear picture on:
- The documentation for CE says that it supports 256 simultaneous connections and offers the Isolation levels, Transactions, Locking, etc with a 4GB DB. But most people say that CE is strictly a single-user DB and should not be used as a DB Server.
Could CE be extended for use as a multi-user DB Server by creating a custom server such as a .NET Remoting Server hosted through a Windows Service (or any other custom host) on a machine whereby the CE DB would run in-process with this server on the machine which would then be accessed by multiple users from multiple machines??
Clients PCs -> Server PC hosting Remoting Service -> ADO.NET -> SQL CE
- and further more can we use Enterprise Services (Serviced Components) to connect to SQL CE and further extend this model to offer a pure high-quality DB Server?
Clients PCs -> Server PC hosting Remoting Service -> Enterprise Services -> ADO.NET -> SQL CE
Seems quite doable to me, but I may be wrong..please let me know either ways
Thanks,
CP
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Jun 19, 2007
I've been following Soctt Mitchell's tutorials on Data Access and in Tutorial 1 (Step 5) he suggests using SQL Subqueries in TableAdapters in order to pick up extra information for display using a datasource.
I have two tables for a gallery system I'm building. One called Photographs and one called MS_Photographs which has extra information about certain images. When reading the MS_Photograph data I also want to include a couple of fields from the related Photographs table. Rather than creating a table adapter just to pull this data I wanted to use the existing MS_Photographs adapter with a query such as...1 SELECT CAR_MAKE, CAR_MODEL,
2 (SELECT DATE_TAKEN
3 FROM PHOTOGRAPHS
4 WHERE (PHOTOGRAPH_ID = MS_PHOTOGRAPHS.PHOTOGRAPH_ID)) AS DATE_TAKEN,
5 (SELECT FORMAT
6 FROM PHOTOGRAPHS
7 WHERE (PHOTOGRAPH_ID = MS_PHOTOGRAPHS.PHOTOGRAPH_ID)) AS FORMAT,
8 (SELECT REFERENCE
9 FROM PHOTOGRAPHS
10 WHERE (PHOTOGRAPH_ID = MS_PHOTOGRAPHS.PHOTOGRAPH_ID)) AS REFERENCE,
11 DRIVER1, TEAM, GALLERY_ID, PHOTOGRAPH_ID
12 FROM MS_PHOTOGRAPHS
13 WHERE (GALLERY_ID = @GalleryID)
This works but I wanted to know if there's a way to get all of the fields using one subquery instead of three? I did try it but it gave me errors for everything I could think of.Is using a subquery like above the best way when you want this many fields from a secondary table or should I be using another approach. I'm using classes for the BLL as well and wondered if there's a way to do it at this stage instead?
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Apr 5, 2007
How do I get a System Table like 'Sysobjects' into the Data Access Layer?
My app generates tables on the fly, and has to check in the sysobjects table which tables are present.
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Jan 10, 2008
Hi Experts ! I want to use maximum feature of SQL
Server 2005 and ASP.Net 2.0 in making Data Access LayerSuggestions will be welcomed .Thank you
RegardsKAMRAN
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Feb 20, 2008
I've a management module (managing Products) currently being displayed on the aspx page using ObjectDataSource and GridView control.The datasource is taken from a class residing in my Data Access layer with custom methods such as getProducts() and deleteProduct(int productID)I'm currently using SqlDataAdapter as well as Datasets to manipulate the data and have no big problems so far.However, my issue is this, each time i delete a product using the deleteProduct method, I would need to refill the dataset to fill the dataset before i can proceed to delete the product. But since I already filled the dataset using the getProducts() method, is it possible to just use that dataset again so that I dont have to make it refill again? I need to know this cos my data might be alot in the future and refilling the dataset might slow down the performance. 1 public int deleteCompany(Object companyId)
2 {
3 SqlCommand deleteCommand = new SqlCommand("DELETE FROM pg_Company WHERE CompanyId = @companyId", getSqlConnection());
4
5 SqlParameter p1 = new SqlParameter("@companyId", SqlDbType.UniqueIdentifier);
6 p1.Value = (Guid)companyId;
7 p1.Direction = ParameterDirection.Input;
8
9 deleteCommand.Parameters.Add(p1);
10 dataAdapter.DeleteCommand = deleteCommand;
11
12 companyDS = getCompanies(); // <--- I need to refill this before I can delete, I would be iterating an empty ds.
13
14 try
15 {
16 foreach (DataRow row in companyDS.Tables["pg_Company"].Select(@"companyId = '" + companyId + "'"))
17 {
18 row.Delete();
19 }
20 return dataAdapter.Update(companyDS.Tables["pg_Company"]);
21 }
22 catch
23 {
24 return 0;
25 }
26 finally { }
27 }
I thank you in advance for any help here.
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Jul 9, 2007
Hi,
I am having a application in which from the front end i am saving details of three different things
i.Enquiry Details
ii.Parts Details
iii.Machine details
i am saving the Enquiry detail in a data table,Parts Details in a data table and machine detail in a data table and finally i am adding the three data tables into a single data set and passing the data set to data access layer there i have three insert command one for each data table in my case the enquiry data table will be saved first and then the next two details will be saved and i am saving the details in three different tables in the database, my problem is some times the enquiry details will save to the database and while saving the Parts details there may be some exception and i will throw an exception in that case the enquiry details will be saved and the remaining two details are not saved(Which are also part of the same Transaction).I wanted to know about how to call the transaction function in case of Data Access Layer.
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Sep 27, 2007
in the class library i written the code name :customer is the lib name
using System;
using System.Collections.Generic;
using System.Text;
namespace Customer
{ class Entites
{
public int inTest;
public int inTest2;
}
}
Now in the Class1.cs i written the code
i am getting the data from the database by using enterprise lib 2006 connection function
now HOW TO BIND THE DATA TO LIST AND RETURN TYPE IS LIST
PLEASE CHECK THE CODE AND REDEFINE THE CODE
using System;
using System.Data ;
using System.Collections.Generic;
using System.Collections.Generic;
using System.Text;
using Microsoft.Practices.EnterpriseLibrary.Data;
using Microsoft.Practices.EnterpriseLibrary.ExceptionHandling;
using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;
using System.Collections;
using System.Xml.Serialization;
using System.Data.Common;
using Customer;
namespace Customer
{
class Class1
{
public List<Entites> getdata(int id)
{
Database db = DatabaseFactory.CreateDatabase("mycon");
System.Data.Common.DbCommand cmd ;
cmd = db.GetStoredProcCommand("GET_CUSTOMER");
cmd.CommandType = CommandType.StoredProcedure;
db.AddInParameter(cmd,"@CID",System.Data.DbType.Int32,id);
List<Entites> objEntites = new List<Entites>();
using (IDataReader dr = db.ExecuteReader(cmd))
foreach (Entites obj in dr)
{
objEntites.inTest = obj.inTest;-----------------------------------------------ERROR LINE
// objEntites.Add(obj);
}
return objEntites;
}
}
}
Error 2 foreach statement cannot operate on variables of type 'System.Data.IDataReader' because 'System.Data.IDataReader' does not contain a public definition for 'GetEnumerator' D:KOTI_PRJSEnterpriseCustomerClass1.cs 34 13 Customer
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Sep 20, 2006
I am taking my first stab at a 3 tier architecture within ASP.Net. I have been adding datasets and creating a new Insert to add certain parts to a table. I am trying to add a date field called 'DateAdded' and is setup in SQL as a DateTime. When Visual Studio auto created the dataset, the Insert function is not "DateAdded as Datetime" as I would have expected, but it is "DateAdded as System.Nullable(Of Date)". There is a space in between 'Of' and 'Date'. If I keep the space in there the insert function shows an error that says "Arguement not specified for parameter DateAdded of funtion( etc. etc.). If I take the space out, the error on the insert function goes away but there is an error within the "OfDate" that says "Array bound cannot appear in type specifiers". I am confused on why the date format changed and how I can get a date to go into the database using the autogenerated datasets from Visual Studio. Any help would be appreciated. Thanks, Mike
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May 19, 2008
Hello,
My datalayer of C# code is invoking a stored procedure that returns a varchar(max) SQL data type. In my ASP.NET code, I have:
SqlCommand myCommand = new SqlCommand("usp_GetTestString", myConnection);
myCommand.Parameters.Add(new SqlParameter("@TestString", SqlDbType.Text));
myCommand.Parameters["@TestString"].Direction = ParameterDirection.Output;
myConnection.Open();
myCommand.ExecuteNonQuery();
return Convert.ToString(myCommand.Parameters["@TestString"].Value);
The query fails to execute and returns an error: String[1]: the Size property has an invalid size of 0. If I change the SqlDbType.Text parameter type to SqlDBType.Varchar, 100 (or any other fixed varchar length), it works but limits the length my unlimited field text. Any suggestions on how I can use db type text or varchar(max)? The field I need to retrieve is string characters of unlimited length and
hence the datatype varchar(max).
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Mar 5, 2006
a number of time I have come accross developers using functions like
GetProduct()
GetProductTitle()
GetProductCategory()
to get the value of the data instead of just using queries / stored procedures
I have not understood why
can you please point to some good forum messages / blogposts / articles on this ?
Whats your take on this ?
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May 26, 2006
In Control Flow you can do that.
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May 21, 2015
Inside of stored procedure you have the code
create table #datatable (id int,
name varchar(100),
email varchar(10),
phone varchar(10),
cellphone varchar(10),
none varchar(10)
);
insert into #datatable
exec ('select *
from datatable
where id = 1')
select * from #datatable
I still want to retrieve the data and present it in the software's presentation layer but I still want to remove the temp table in order to reduce performance issue etc.
If I paste the code DROP
TABLE #datatable after
insert into #datatable
exec ('select *
from datatable
where id = 1')
Does it gonna work to present the data in the presentation layer after removing the temp table?
The goal is to retrieve the data from a stored procedure and present it in the software's presentation layer and I still need to remove the temptable after using it because I will use the SP many time in production phase.
[URL]
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Sep 22, 2015
I'm trying to re-write my database to de-couple the interface (MS Access) from the SQL Backend. As a result, I'm going to write a number of Stored Procedures to replace the MS Access code. My first attempt worked on a small sample, however, trying to move this on to a real table hasn't worked (I've amended the SP and code to try and get it to work on 2 fields, rather than the full 20 plus).It works in SQL Management console (supply a Client ID, it returns all the client details), but does not return anything (recordset closed) when trying to access via VBA code.The Stored procedure is:-
USE [VMSProd]
GO
/****** Object: StoredProcedure [Clients].[vms_Get_Specified_Client] Script Date: 22/09/2015 16:29:59 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
[code]....
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Feb 16, 2005
what is the best way to create a MS SQL 2000 database from an existing MS ACCESS 2003 database
with all datas in it ?
thank you
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Feb 25, 2004
I'm currently writing a web application in Coldfusion which uses a Access 2000 db. I can create tables in SQL ok but am having problems with the Autonumber type. Any ideas?
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Mar 1, 2006
I am trying to create a MS Access datasource to use it in a IS dataflow. I've done the following things:
1.I've created an ODBC datasource - System DSN, pointing to the Access database.
2.I've created an ODBC connection manager pointing to the ODBS datasource that I created in the previous step.
3.I've created a DataReader Source that uses as its Connection Manager the connection manager that I created in the previous step.
I get the following error message: "Cannot acquire a managed connection from the run-time connection manager." What can I do to solve this error?
Pedro Martins
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Nov 8, 2007
Hello,
Is anyone using an abstraction layer for the middle tier to interface with so the actual table design is hidden for the application? I have read several articles that it can be done using views http://www.sqlservercentral.com/articles/Database Design/61335/. However, I don't see myself creating a view ontop of every table and allowing dml modifications to happen through them. I think it would make the query optimizier throw up after a certain level of data and views are encountered. I know snonyms are available in 2005, but I have only seen what can be done not what should be done.
I don't have a fear of allowing my .NET developers (I work with very competent people) to create middle tier objects directly against the db tables for oltp dml operations. I don't want to create stored procedures for these because I think more flexibility exists within the middle tier for business logic. Then all select operations are performed against the db with stored procedures. Does anyone out there think I am crazy? Has anyone successfully created an abstraction layer strategy for their entire db?
Thanks!
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Mar 15, 2007
What is Persistance layer?
And is it part of Database layer or other name for database layer?
--Deepak
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Jun 30, 2015
I have a client who has SSMS installed on her laptop. She is able to connect to the SQL server via SSMS in the office and query data on the server.
She needs to be out of site often and doesn't have internet access. She asks if the data tables can be "backed up" or saved on her laptop, so she can look at them without worrying connecting to the server. I am not sure if this can be achieved, as SSMS is built for accessing a server, not a desktop. Myself never have this need. If I really need it, I would go to Microsoft Access and create an ODBC connection to the datatables. But this client thinks that Microsoft Access is beneath her.
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Jul 20, 2015
HowTo: Import data to MS SQL 2008 from password protected Access DB ?
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Jan 13, 2004
I'm trying to create a linked server to an Access database that resides on a separate machine.
On my PC, I can create a link to the Access db, and view, update, add and delete data. If I create the same linked server on our production Server, I can again view, update, add and delete data. All's well so far.
If I now go back to my own PC (used for developing) I cannot access the linked server on the production machine.
The Access database is stored on a separate PC, so the I'm linking to a remote db. As I said this works fine if I'm sat in front of the PC that the linked server is created on - but not if I use a client PC to connect.
I create the linked server using the following command:
exec sp_addlinkedserver
@server = 'AccLinkedServer',
@provider = 'Microsoft.jet.OLEDB.4.0',
@srvproduct = 'OLE DB Provider for Jet',
@datasrc = '\DatabaseServerAccessDatabase.mdb'
If I run the SQL statement:
SELECT * FROM AccLinkedServer...AnyTableYouLike
I get this error:
Server: Msg 7399, Level 16, State 1, Line 1
OLE DB provider 'Microsoft.Jet.OLEDB.4.0' reported an error.
[OLE/DB provider returned message: The Microsoft Jet database engine cannot open the file '\DatabaseServerAccessDatabase.mdb'. It is already opened exclusively by another user, or you need permission to view its data.]
OLE DB error trace [OLE/DB Provider 'Microsoft.Jet.OLEDB.4.0' IDBInitialize::Initialize returned 0x80004005: ].
I've searched in the MS knowledge base, and this forum and followed all of the advice that was available, but it still won't work.
Anyone got any other advice, before I go totally insane with this.
Cheers.
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Mar 19, 2008
Hi!
This is quite weird.
When I first wanted to create assably using:CREATE ASSEMBLY hashfrom 'C:hash.dll'WITH PERMISSION_SET = EXTERNAL_ACCESS... Server returned error:CREATE ASSEMBLY failed because it could not open the physical file "C:TESTS_Run_This_In_SQL2.dll": 2(The system cannot find the file specified.).Then I tried to find file with exec Master.dbo.xp_fileexist 'C:hash.dll'File exists - falseFile is directory - falseParent directory exists - trueConclusion: Server knows that I have hard drive but cannot see the file (by the way file IS THERE 10000%,alright)
2nd TRY:Copy file to a Server PC named 'pluto' in a directory... i try to create an assably:CREATE ASSEMBLY hashfrom '\plutoProjektiECDLhash.dll'WITH PERMISSION_SET = EXTERNAL_ACCESS...SAME THING: The system cannot find the file specified.i try to find file.... SAME THING!
3rd TRY:I copy file to another Server PC, this time i try to find file first:exec Master.dbo.xp_fileexist '\Depoprojekti2ECDLSRCBackuphash.dll'IT WORKS!!! file is found!!! now everything should work....right!CREATE ASSEMBLY hashfrom '\Depoprojekti2ECDLSRCBackuphash.dll'WITH PERMISSION_SET = EXTERNAL_ACCESS.....CREATE ASSEMBLY failed because it could not open the physical file "\Depoprojekti2ECDLSRCBackuphash.dll": 5(Access is denied.).
Now this is fun.
The whole point of this is can somebody tell me what permissions I (or Management Studio or whatever) have to have in order to create an assably from dll?
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Mar 13, 2007
Hi
I am trying to create an access database (vb 2005). The code sample below works fine if I create the database without specifying a username and password (values left blank). However if these are specified an exception is thrown. Any help/suggestions would be appreciated.
Try
Dim cat As Catalog = New Catalog()
cat.Create("Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=C:Seans VBAppGeneratorSystemAppGen.mdb;" & _
"Jet OLEDB:Engine Type=5;" & _
"User Id=user;" & _
"Password=pass;")
Console.WriteLine("Database Created Successfully")
cat = Nothing
Catch ex As Exception
Console.WriteLine("Failed to create database")
End Try
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Sep 15, 2006
How do you create a link to MS Access DB in SQL Server 2005. Thanks
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May 23, 2007
I have the following stored procedure:
INSERT INTO MyTable ( Value1, Value 2)
VALUES( @Value1, @Value2)
SELECT SCOPE_IDENTITY()
How do I put this sp in the DAL typed dataset, so I can get the Identity value in the Business Layer?
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Jun 12, 2008
Can I use this class in ASP.NET web site with many visitors?SqlLayer.cs: public static class SqlLayer{ public static string ConnectionString = ConfigurationManager.ConnectionStrings["SomeConnectionString"].ConnectionString; public static int ExecuteNonQuery(string StoredProcedureName, string[] ParamNames, object[] ParamValues) { if (ParamNames.Length != ParamValues.Length) { throw new Exception("ParamNames.Length != ParamValues.Length"); } using (SqlConnection cSqlConnection = new SqlConnection(ConnectionString) { cSqlConnection.Open(); SqlCommand cSqlCommand = cSqlConnection.CreateCommand(); cSqlCommand.CommandType = CommandType.StoredProcedure; cSqlCommand.CommandText = StoredProcedureName; cSqlCommand.Parameters.Add("@ReturnValue", DbType.Int32); cSqlCommand.Parameters["@ReturnValue"].Direction = ParameterDirection.ReturnValue; for (int i = 0; i < ParamValues.Length; i++) { cSqlCommand.Parameters.AddWithValue(ParamNames[i], ParamValues[i]); } cSqlCommand.ExecuteNonQuery(); return (int) cSqlCommand.Parameters["@ReturnValue"].Value; } } public delegate void ActionForReader(SqlDataReader Reader); public static void ExecuteReader(string StoredProcedureName, string[] ParamNames, object[] ParamValues, ActionForReader cActionForReader) { using (SqlConnection SqlConnection1 = new SqlConnection(ConnectionString)) { SqlConnection1.Open(); SqlCommand SqlCommand1 = SqlConnection1.CreateCommand(); SqlCommand1.CommandType = CommandType.StoredProcedure; SqlCommand1.CommandText = StoredProcedureName; for (int i = 0; i < ParamValues.Length; i++) { SqlCommand1.Parameters.AddWithValue(ParamNames[i], (ParamValues[i] == null ? DBNull.Value : ParamValues[i])); } using (SqlDataReader Reader = SqlCommand1.ExecuteReader()) { if (cActionForReader != null) { //if (Reader.HasRows == false) throw new Exception("Reader has no rows"); //if (Reader.RecordsAffected == 0) throw new Exception("Reader RecordsAffected = 0"); while (Reader.Read()) { if(Reader!=null) cActionForReader(Reader); } } } } }} Using: SqlLayer.ExecuteNonQuery("SomeStoredProcedure", "ID", ID);---------SqlLayer.ExecuteReader("SomeStoredProcedure", new string[]{"Param1","Param2"}, new object[]{Value1,Value2}, Action);...void ActionForForumCollection(SqlDataReader Reader) {LabelContent.Text += Reader[0].ToString()+" - "+Reader[1].ToString();}
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Aug 17, 2007
Instead of showing the same content (images) when customers visit our application, we want to show random images to make use of all the images that can be displayed.
My question is, is it better to handle randomness at SQL or in the application layer. In sql, we can achieve this by doing order by newid(). My understanding of this is, SQL will create a guid (which is random) for all the rows in the resultset and will sort by the guid. If this code is encapsulated in a SP and if it may be executed over say 200+ or say 1000+ times a day, isn't it better to handle the randomness in the app layer. Let the app layer use resources and sql just retrieve the data necessary.
Any thoughts?
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Feb 19, 2008
Hello,
I'm searching for good documentation for building Application layer for Report (SSRS) using Visual Studio 2005. Kindly forward useful link if possible or walk me through.
Thanks,
Monika
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Oct 26, 2000
Hi, Folks!
I'm receiving Access Violation Error when I'm trying to create a clustered index on a datetime field on a table that have around 4 million records, if I create the index nonclustered, no problem, but clustered the system raise this error!
Any help will be appreciate a lot!
Thanks in advance!
Armando Marrero
Cti. Miami
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