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Hi Boycech. Using Access the way you're describing isn't a bad way to start getting to know SQL - just be aware that Access' flavor of SQL isn't exactly ANSI-compliant. Access is also notorious for generating sql statements that are far more verbose than they need be - downright confusing at times.
If you're really just getting started with SQL, take a look at the W3Schools Sql Tutorial[^]. You might find it useful.
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Howdy,
A few random bits of advice: 1) You are dead-right: study up on SQL. 2) Make use of stored procedures (aka: sprocs). I don't know if there is an Access equivalent, but in sql-server a sproc is like a function call: you pass it parameters when you call it, it does some voodoo (run sql code) on the database and returns a record set (if you need it to). The big advantage to sprocs is that your ASP code doesn't rely on how you implemented things in the database. Think of them as a layer of insulation between the GUI and the data. So 6 months from now when you need to change something on the database, all you need to do is adjust the code in the sprocs to assure that they all still return the same data. Otherwise a design change on your database might break A LOT of your GUI.
Bill
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Access (at least the 2003 version) does support Stored Procedures - only in an ADP Project, using an SQL database as the backend. I used Access to learn SQL, so I would reccomend it for any real beginner.
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Hi,
I'm writing a program based on an Access Database.
I need to create this database while installing the Application Installer.
While reading Visual Studio documentation, I saw I have to use the SQL Keyword CREATE DATABASE. This is ok for Sql Server, but not for Access.
How can I do ? 
Any idea is welcome.
Thanks.
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There is an easy way with DAO: CDaoDatabase::CreateDatabase... I know you posted it this in the ADO section but this could be an easy way out!
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Not exactly. If you try to mix ADO and DAO, you normally get a ton of conflicts. More specifically, the DataType enum seems to have been defined in both libraries, and they are not compatible. That is the voice of experience  speaking!
ADOX supposedly has a Create function in its catalog class that can be used to create a database at run time. I have not had much luck with it yet. Perhaps Carlos Antollini (of CADOXxxx classes fame) may have an answer? I read that he has an update to his ADOX classes about ready. I sure am looking forward to it.
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This seems to work fine with an abbreviated Connection string.
You can not use the full-blown connection string.
I just tested it and it created the database successfully. Probably not the most efficient error reporting, but that you can modify to suit your needs.
The CADOXCatalog comes from Carlos Antollini's ADOX class available on CodeProject website.
------------------------------------------------------------------------
CString sConnectionString = _T("Provider='Microsoft.Jet.OLEDB.4.0';Data Source='%s'");
CString sMsg;
try
{
CADOXCatalog cat;
CString sConnect;
sConnect.Format (sConnectionString, sDBName);
cat.m_pCatalog->Create(_bstr_t((LPCTSTR) sConnect));
sMsg.Format (_T("Database %s created successfully"), sDBName);
}
catch (_com_error& e)
{
TCHAR szBuf[300];
// Notify the user of errors if any.
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
sprintf(szBuf, "Source : %s\nDescription : %s", (LPCSTR)bstrSource,(LPCSTR)bstrDescription);
CString sErr = CString (szBuf);
sMsg.Format (_T("Can not create database %s\n%s\n%s"), sCmd, CString (e.ErrorMessage()), sErr);
}
AfxMessageBox (sMsg);
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Has anyone use connected sucessfully to Sage using there shipped driver?
You can query all of the tables using Excel, but can't using either vb6 or vb.net.
Thanks in advance.
Wayne Taylor
Kryptos Solutions
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Hi there
i have a stored procedure like this:
CREATE PROCEDURE SP_Main
AS
SET NOCOUNT ON
BEGIN TRANSACTION
exec SP_Sub_One output
exec SP_Sub_Two output
IF @@ERROR = 0
BEGIN
-- Success. Commit the transaction.
Commit Tran
END
ELSE
Rollback Tran
return
GO
now the problem is, when i execute the stored procedure's inside the main stored procedure, and these sub sp's has an error on it, the main stored procedure doesnt rollback the transation.
now i can put the "begin transation" in the two sub stored procedure's. The problem is
what if the first "SP_Sub_One" executed successfully, and there was error in "SP_Sub_Two"
now the "SP_Sub_One" has been executed and i cant rollback it... the error occured in the
"SP_Sub_Two" stored procedure ... so it wont run ... so there will be error in the data
how can i make a mian "BEGIN TRANSACTION" , that even it include the execution of stored procedure in it.
Thanks in advance
Mahmoud Manasrah
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Check out this transaction documentation from the MSDN site.
Note especially this paragraph:
Naming multiple transactions in a series of nested transactions with a transaction name has little effect on the transaction. Only the first (outermost) transaction name is registered with the system. A rollback to any other name (other than a valid savepoint name) generates an error. None of the statements executed before the rollback are in fact rolled back at the time this error occurs. The statements are rolled back only when the outer transaction is rolled back.
Over time, I've learned to always use named transactions as a matter of course. When I use them in stored procedures, I often name them after the procedure; so in procedure pr_execute_code_a, I'd probably use
BEGIN TRANSACTION peca
This only minimizes the chance of a naming conflict, so you still have to be careful, but you get the idea. With named transactions, you're free to wrap stored procedures in other ones at will and still guarantee data integrity; the inner stored procedures can roll back just their own data if that's appropriate, and the outermost procedure has complete control over its own transaction; it can roll everything back or not.
When I am creating an "open" stored-procedure API, I always make sure that the procedure returns some non-zero value (always 1 if I'm not returning specific error codes) in case of an error, in addition to a RAISERROR call and/or a rollback of a transaction. That way calling code (which may be an enclosing procedure) has enough information to roll back a transaction. You know how to get this from an EXECUTE statement, right?
<br />
DECLARE @returnCode AS INT<br />
<br><br />
-- ...<br />
-- ...<br />
<br><br />
EXEC @returnCode = pr_DoSomething<br />
--<br />
IF (@returnCode <> 0) BEGIN<br />
-- roll back your transaction, if appropriate<br />
-- raise an error, if appropriate<br />
RETURN(1) -- if appropriate<br />
END -- IF<br />
In your case, if you're the one controlling and using the code and the inner procedures are always called by some other, you may not need transactions in your inner procedures at all, only in the outermost one(s).
Regards,
Jeff Varszegi
EEEP!
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Hi Jeff ,
Thank you alot of ur reply, it was reallly great
Wish u luck
Thanks Alot
Mahmoud Manasrah
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I am using a dateset.
Heres the problem:
Lets assume theres a table T, with one row in it. I populate my dataset by using Fill().
In my software I now delete the row (from the dataset only).
If I use the Update() with the dataset, the row will be removed from the DB. This is fine.
But what happens if I do this:
1) Call Fill() to populate the dataset.
2) Delete the row from the dataset.
3) Add a new row to the dataset.
4) Delete this new row again.
The problem is that there will now be two rows in the dataset that is flagged to be deleted when Update() is called. But only one of these will be in the database!
If I call Update() now, the system will try to delete both from the DB, but since only one of them is available in the DB to delete, a Concurrency exception will be thrown (since no rows will be affected when the system tries to delete the nonexistant row).
What is the best practice in these kind of situations?
Thanks for your time.
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I am having to come up with factors that may be involved when you are transferring data from one database architecture to another. In other words, if I wanted to transfer to RDBMS from a network architecture what do I need to look for?
How can I find out this information - if I wanted to research? I have been trying to find it, but I must be putting in the wrong keywords for my search.
Thank you,
ibok23
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Hi,
How do I check whether a login exists for a particular database in MSDE?
Code:
SqlConnection objConn = new SqlConnection(strCon);
objConn.Open();
SqlCommand objCmd = new SqlCommand();
objCmd.Connection = objConn;
//eg: if login 'priya' does not exist in database PRIYA how do i do it
objCmd.CommandText = @" EXEC sp_addlogin @loginame ='abb',@passwd ='abb',@defdb = 'ABB' EXEC sp_grantdbaccess N'abb', N'abb' EXEC sp_addrolemember N'db_owner', N'abb'" ;
objCmd.ExecuteNonQuery();
Thankx in advance
Priya
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One thing that come to my mind now is using sp_who which return information about users and if the given name does not exists, it retun 1.
Mazy
"One who dives deep gets the pearls,the burning desire for realization brings the goal nearer." - Babuji
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sp_who only shows logged in users, not all existing users
Jeff Martin
Triple20 Software
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2 quick ways to find out if a user exists in SQL Server.
1) check the sysusers table:
select count(uid)
from sysusers
where name = 'NameYouAreSearchingFor'
if it returns 0, the user doesn't exist. But since MS doesn't recommend querying the sys tables directly (so they can change in later versions), you should use #2
2) use the sp_helpuser stored proc
exec sp_helpuser 'NameYouAreSearchingFor'
if it returns something, your user exists.
Jeff Martin
Triple20 Software
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Hi,
How do I check whether a database exists before attaching a database ?
Thankx in Advance.
Priya
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IF (NOT(EXISTS(SELECT * FROM master.dbo.sysdatabases WHERE [name] = 'Northwind'))) BEGIN
-- attach your database
END -- IF
This information only applies to SQL Server. This is just off the top of my head-- not using databases today. You might poke around throught the INFORMATION_SCHEMA views to see if there's some view containing that stuff too; Microsoft always recommends using the information schema over accessing system tables directly.
Regards,
Jeff Varszegi
EEEP!
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Will this allow checking for a database that doesn't have any tables?
Regards,
Jeff Varszegi
EEEP!
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It should. I haven't tested it, but I don't see why it wouldn't work. information_schema is just a view into the system tables.
Jeff Martin
Triple20 Software
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