Database Logic - Differences Between Datasets And Datatables ?
Jan 12, 2009
My understanding of databases (access and sql) is fairly limited, though i have got a couple of programs under my belt using access databases, not yet used SQL. I could however, work around to figure out a way to do what i'm trying. What i don't understand is the need for all of the components, so all i'm after is somebody who can take the time to fully explain these further to me, or point me in the direction of somewhere i can gather a full understanding.
My questions are, for now;
1. Why do we need to take a copy of the database, rather than dealing exactly with the database itself?
2. What differences are there between datasets and datatables, what is better for what and why?
3. What is the purpose of the data adapter?
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Mar 10, 2010
How To Join Two Datatables From Different Datasets (With One Commn Column) ???
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Jun 1, 2012
I'm having a hard time joining 2 datatables and have the joined datatable as result. First datatable (labels) holds data including a printerid. Second datatable (printers) holds printer references (id > unc). I would like to have as endresult (joined) a datatable with all data from the first datatable with the field (unc) of the second datatable. [Code]
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Apr 8, 2010
i need to make a database application that can write/retrieve cells/datasets from/to a database i buyed a book in there was an example of how to create a database application while debugging i had the "Object reference not set to an instance of an object." error and it highlighted this code
objDataRow = objDataSet.Tables("KlantenTable").NewRow
now the problem is here i declare something later in the code i write to it
objDataSet.Tables("KlantenDataTable").Rows.Add(objDataRow)
[Code]....
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May 2, 2010
How can i write logic to check is it my sql statement being insert into my database ? is there any ways to create or thing can check thru by using webservice?
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Sep 16, 2008
I would be grateful if someone could explain how to highlight differences in html text which is pulled from an SQL database in VB ASP.net.I want to compare two rows of similar text in the database and highlight the paragraphs/areas which are different to display changes of previous versions of the text on a web page to the user.
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Aug 27, 2010
I have two small VB.NET applications that connect to the same Oracle database. One uses the OLEDB provider, and the other uses Oracle's ODP.NET. Should I expect to see problems with the OLEDB provider, as it's less 'native' to Oracle?
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Jun 13, 2011
I have two DataTables that come from two tables in an Access 2007 database. The first is my table for car data and it has been populated with a process that reads text data. i can use this table and update the db and no problems. However the car data table also needs those cars even when no points where collected. So I have a control table that has a list of all cars. Now i have two tables and if I use the .Merge function I get a third table with both sets of data. But when i try to update the db with this third table I get an error "System.InvalidOperationException: Dynamic SQL generation for the UpdateCommand is not supported against a SelectCommand that does not return any key column information.
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Sep 6, 2010
this is my code and it has an error "Command text was not set for the command object."Dim con As OleDb.OleDbConnection = New OleDb.OleDbConnection()
Dim sSql As String
Dim command As OleDb.OleDbCommand = New OleDb.OleDbCommand(sSql, con)
Dim adapter As New OleDb.OleDbDataAdapter(sSql, con)
[code].....
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Jan 19, 2010
I have a table, lets call it Objects. It has a predefined set of records looking like this:
ObjectId ObjectName
1 Salmon
2 Trout
3 Seabass
4 Shark
Etc..
So, this I would like to implement somehow as an enum. But what's the best way, implement it in the database creating tables for it or in the application logic in an CommonEnums codebehind file etc?
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Jun 2, 2011
I've been having a problem adding a record to an Access database using datasets and da.update etc. I'm trying to create a simple program that displays the records of a database table in a series of text boxes. I've managed to get my next and previous buttons working correctly and my update button works correctly too. The problem occurs when I try to add a new record. I keep getting a "Syntax error in INSERT INTO statement" whenever I click my add button.
[Code]...
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May 13, 2010
I have an application that uses an access database to fill datasets. My problem is that I have three related tables, when I add a new users to the customers table The parts table fills with data saved in the database with a cust_id of -1.
I discovered that this is caused by adding a part, not saving it and deleting the customer. I Can add code to stop the user from deleting a customer that has parts but I do not have access to the live database to delete the record that are incorrect.
Is there something I can do to delete the rows that have an id of -1 on the load statment?
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Sep 3, 2010
The application uses ADO.NET to invoke sprocs for nearly every database operation. Some of these sprocs also contain a fair amount of domain logic. The data access logic for each domain entity resides in the domain class itself. ie, there is no decoupling between domain logic and data access logic. I'm looking to accomplish the following:
[Code]...
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Dec 23, 2011
I already know how to call insert, update, delete & select procedures in DataSet.xsd window. And I also know how to call queries by table adapters. But I just found out that its not possible to call all functions by queries (such as insert). It works when I test the query but when I try to add it, it says "Failed to get schema for this query". So I built a few stored procedures which do many functions (such as transaction, insert, update etc...). But I am unable to use these stored procedures in VB form. I found some tutorials mentioning that it can be done by defining connections and some other stuffs with which I don't want this to be. I want to call these procedures by writing code in VB code editor window with DataSets, TableAdapters, BindingSource etc...
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Jul 6, 2009
Am I on the right path I programmatically create, fill, modify, essentially communicate with a set of Datatables, etc within my app while never having an actual database (i.e. Access.mdb file) all residing in memory but never really existing in an '.mdb' file, for example?
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Aug 22, 2010
What are the differences between 32 and 64-bit .NET (4) applications?Often 32-bit applications have problems running on 64-bit machines and conversely. I know I can declare an integer as int32 and int64 (certainly int64 on 32-bit systems make problems). Are there other differences between programming an 32 OR 64-bit or a both 32 AND 64-bit compatible application?
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Aug 10, 2010
Would like to build an application and was wondering why someone would choose one language over another.Also is one language used more for a particular type of programming then another (For example, is VB used more for business or Windows development then for web development ?)
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Aug 14, 2009
I am currently learning visual basic 5 on my home computer. I was wondering if someone could tell me what the major differences are between Visual basic 5 and the latest/new editions of VB.
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Jan 14, 2010
We have legacy character codes that we want to store as numbers in a new system. To increase readibility and general understanding in the code for devs making the migration, I want to do Enums like this..
[Code]...
With this setup, the code will be readable (imagine If Record.Status = Status.Open), and yet the values will be stored in the database as small numbers so it will be efficient. However... I am a VB.NET guy, but everybody wants to code in C#, so I need this sort of structure in C#.After Googling, I discovered the the general .NET equivalent of AscW is Convert.ToInt32("C"). When I try to use that statement in an enum, I get the compiler error "Constant Expression Required".
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Dec 13, 2011
in order for me to get help on me and my programming partners vb6 rpg, I have to upgrade the project to the vb.net platform, and I am worried that the IDE interface that is used to program the vb side of the rpg is different, so I am wanting to ask any of you if there are any significant changes to the IDE or if it is relatively the same as it was in vb6... I am also hoping that someone here can also help me to see what is wrong with my load/save function... I now thought of something to try to see if that is the issue or not, but the code is still vb6 code, the only difference will be that the program will be upgraded to the .net platform, so if that changes anything in the code, then I am not aware of this as of yet, because I am still downloading the visual studios 2010 express iso right now... so I do not know for sure yet what will be changed.
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Dec 18, 2011
Does anyone know how to implement in VB an algorithm for final differences that changes the network (the matrix) during the computation (decrease its dimensions)?
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Aug 26, 2011
Today I was playing around with Entity Framework and I've read that the generated IL for C# was different than VB.NET for the following code:
[code]...
As it seems the VB.NET version of this code will contact the database every time the code is executed while the C# version will retrieve the entities from the cache when the code is executed multiple times.Why would they make both languages behave in such a different manner?It was my misconception that both languages just differed in syntax and had almost exactly the same generated IL.Are there any more examples where both languages generated such different IL?
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Jan 17, 2011
what can C# do that VB.Net can't ? VB.net vs C#.net
main differences between visual basic and C# as well as the pros and cons between the two?
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Nov 11, 2011
I'm trying to the contents of a datatable to a datatable thats allready in my form using the openfiledialog.[code]...
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Apr 12, 2010
I'm trying to create a program that will merge two data tables (one from a database on a network drive, the other is found in a database on the local machine). Each datatable is identical in structure, only (maybe) differs in content. The structure has a primary key, dateCreated, and dateLastEdited fields (plus other fields). I would like to merge down from the network to the local database. If the primary key does not exist on the local db but does on the network, copy from the network db to the local table. If it does exist, check the dateLastEdited column and copy the latest row to the local table.
How would i set up the code to do this? Any assistance would be great.
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Jan 23, 2012
How to intersect two dataTables in vb.net 2.0? I want to get common rows in two datatables and add it in third datatable.
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May 20, 2012
I need to marge two datatables with condition. I have a datatable where the data comes from a local XML Database and another datatable where the data comes from a remote SQL Server. If any update made in the remote datatable I need to update/merge with the local datatable. Here is what I have so far:
Public Sub MargeTwoTable()
Dim SQL As String = ""
Dim RemoteTable As New DataTable
Dim LocalTable As DataTable
[code]....
In this code data comes from the remote database which updates a date getter then the local database . Both tables have "ID" as the primary key. The code is working well, but the problem is that when more than 1000 records are updated this function takes too long using loops.
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May 28, 2012
I have two datatables which I intends to bind them to Gridview. But I need bit of the first dt and bit from second dt.
Second table has only one row that represents to every row in the same column in first table.
There is no primary key or relationship between two tables though.
For example,
I tried datatable.merge though. Didn't produce the last table i want.
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Jun 7, 2012
I have a Main Table that contains all the distinct values in a DataTable.DataColumn. also have a Child Table that contains distinct values created by the user.I want to merge the Child Table DataRows that match on the Value column with theMain Table DataRows to create the New Table (shown below).I want to preserve the values in the Selected column of the Child Table.Here is my problem, if I use the DataTable.Merge method the DataRow that contains "888" in the Child Table is added to the New Table, but it doesn't contain a RowState = Added, thus I can't filter for added rows to remove them.
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Jun 10, 2010
I am using VB Express 2008 and SQL Server Express 2008.I have one DataGridView on a Windows Form, which I am attempting to populate from two datatables. Both tables are identical in structure, but with data from two different dates. The respective SELECT statements are identical, except for the date; one calls for yesterday, one for today. I need a seperate Sum column from each table.I've tried to JOIN, UNION, and MERGE the tables, but that gives me all the data consecutively and I saw no way to seperate the days. I'm able to add DataColumns, and sum the fields with an expression, but is it possible to create DGV columns and bind them to the seperate DataTable columns? [code]
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