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thanks  so I run this as a nonquery?
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I keep getting an error about an "Unrecognized escape sequence" this is the line
SqlCommand cmd1 = new SqlCommand("EXEC sp_addumpdevice 'disk','databasedump','C:\temp\database.dat")
What am I doing wrong?
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If you're using C#, you need to either prefix the string with @, or you need to double the backslash characters - the \ character begins a special character combination in all C-based languages. See the documentation for string[^] or the specification for string literals[^] (although this is probably too much detail!)
Specifically, the '\t' will be interpreted as a TAB character and '\d' is causing the error you mention (since this is not a valid escape).
You also appear to be missing a single-quote mark to close the last string parameter.
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ok I thought that's what it was but I got sidetracked on another project and never had time for it untill today (what good timing huh  )
I am trying to do the backup command you showed me and I am delaring them like this
<br />
SqlCommand cmd1 = new SqlCommand("EXEC sp_addumpdevice 'disk','localBackup','C:\\temp\\database.dat'",sqlConnection1);<br />
<br />
SqlCommand cmd2 = new SqlCommand("BACKUP DATABASE databaseName TO localBackup",sqlConnection1);<br />
I am calling them from within this try block
<br />
try<br />
{<br />
cmd1.ExecuteNonQuery();<br />
cmd2.ExecuteNonQuery();<br />
tbError.Text = "Finished";<br />
}<br />
and running them as non queries (I tried them as transactions but it gave me this error "The procedure 'sp_addumpdevice' cannot be executed within a transaction")
so I took them out and make them queries and now I get a problem with the Execute command saying I need a transaction property.
"Execute requires the command to have a transaction object when the connection assigned to the command is in a pending local transaction. The Transaction property of the command has not been initialized."
Now I am really confused 
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I suspect you've still got a BeginTransaction call outstanding on the sqlConnection1 object.
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As the subject suggests, I'm simply updating the database with SqlDataAdapter.Update and sometimes no update occurs, but usually it does. If it never worked, I'd know it was a problem with my code, but running twice the same steps doesn't always produce the same results.
I've read on the web that others have seen this behavior but haven't seen any fix or workaround. Anyone here experienced this or know a workaround?
-- James --
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So I'm happy to report the problem was with my code and not with the .NET SqlDataAdapter. But I think the circumstances of the problem bear repeating so that others might avoid it.
Form A creates some SqlDataAdapters that fill a dataset and periodically refreshes it. At some point, due to user interaction, an instance of "Form B" is created and passed a reference to the SqlDataAdapters. Form B then finds a DataRow in one of the tables of the dataset, does some work on it, and then calls SqlDataAdapter.Update to put the changed DataRow in the database. And this worked _most_ of the time, but occasionally it would not - no data would be updated to the database.
It turns out that during Form A's periodic update, it would clear the datatable and the refill it. This process would cause Form B's datarow it was working on to get to a state of DataRowState.Detached. Since the DataRow was now detached, when form B would call SqlDataAdapter.Update, the info from the row would not go to the database because the DataRow is not associated with the DataSet that the adapter was working with. And there was no error to be reported in this circumstance.
So the moral of the story is this: Beware what's happening to your DataSet or DataTables while working with a DataRow. And it doesn't hurt to make sure the row hasn't somehow become detatched when you weren't watching.
-- James --
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I have 2 tables:Table1 and Table2 where I have ID and Dateentered.
The both tables can have the same id but different date.
If record in table 1 is oldest then in table2 select data in table1.
How do I do this?
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Assumption: you mean that you want to select the rows which have the lowest date, whichever table they come from.
On this assumption, I think doing a UNION of the tables is probably about right.
SELECT [ID], MIN( Dateentered ) AS MinDate
FROM Table1 UNION ALL Table2
GROUP BY [ID] If you actually want to insert rows or update rows in table 2, that's a bit trickier, and would have to be done in two stages:
-- Insert any rows into Table2 that are in Table1
-- but not in Table2
INSERT INTO Table2
SELECT T1.[ID], T1.Dateentered
FROM Table1 T1
LEFT JOIN Table2 T2 ON T1.[ID] = T2.[ID]
WHERE T2.[ID] IS NULL
-- Set Table2's entries to the date in Table1,
-- if table1's are earlier
UPDATE Table2
SET Dateentered = T1.Dateentered
FROM Table1 T1
INNER JOIN Table2 T2 ON T1.[ID] = T2.[ID]
WHERE
[ID] = T1.[ID] AND
T1.Dateentered < T2.Dateentered
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Hello,
I wonder if anyone can help me with this.
I try to insert a record in a DataTable, and everything works absolutely perfect. UNTIL I create a custom DataView object based on the table.
Here is a small sample, when you take the DataView myView = new DataView(table); line out of comment the record isn't at the correct position anymore.
Any help is much appreciated !!!!
DataTable table = new DataTable("Table");<br />
<br />
DataColumn colID = table.Columns.Add("ID", typeof(int));<br />
DataColumn colName = table.Columns.Add("Name", typeof(String));<br />
<br />
colID.AllowDBNull = false;<br />
<br />
table.Rows.Add(new object[] {1, "Row 1"});<br />
table.Rows.Add(new object[] {2, "Row 2"});<br />
table.Rows.Add(new object[] {4, "Row 4"});<br />
<br />
table.AcceptChanges();<br />
<br />
<br />
foreach(DataRowView row in table.DefaultView)<br />
{<br />
Console.WriteLine(row["Name"]);<br />
}<br />
<br />
Console.WriteLine("-------------------------------------------------------");<br />
<br />
DataRowView cindyView = table.DefaultView.AddNew();<br />
cindyView["ID"] = 3;<br />
cindyView["Name"] = "Row 3";<br />
<br />
Object[] ItemArray = cindyView.Row.ItemArray;<br />
cindyView.CancelEdit();<br />
<br />
DataRow cindy = table.NewRow();<br />
cindy.ItemArray = ItemArray;<br />
cindy.EndEdit();<br />
table.Rows.InsertAt(cindy, 2);<br />
<br />
table.DefaultView.RowStateFilter = DataViewRowState.None;<br />
table.DefaultView.RowStateFilter = DataViewRowState.CurrentRows;<br />
<br />
foreach(DataRowView row in table.DefaultView)<br />
{<br />
Console.WriteLine(row["Name"]);<br />
}
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It would help if you posted the actual output from this code and what you expected to see.
IIRC, unless you've applied a primary key constraint, or some kind of sort criteria, your view will show the records in the order they were inserted.
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I get the following output if I don't create the additional DataView:
Row 1
Row 2
Row 4
-----
Row 1
Row 2
Row 3
Row 4
And this is the output when the DataView object is created based on the table:
Row 1
Row 2
Row 4
-----
Row 1
Row 2
Row 4
Row 3
I don't see, why the DevaultView of the table changes the order of the DataViewRows, just because I create another DataView object based on this DataTable. Also, when I go in debug mode and check the Rows collection of the DataTable, the rows appear as one would expect (1, 2, 3, 4).
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Hi
I have a datagrid bound to a dataset. I can insert and update thru the grid but a delete returns the following message (through OleDbException.Message)
"Incorrect syntax near the keyword DEFAULT"
This is thown when I call the OleDbDataAdapter.Update() method using my dataset as the target. The following is my code for the delete command of the dataAdapter:
<br />
string sql = "DELETE FROM Product " +<br />
"WHERE productID = ? AND desription = ? AND " +<br />
"cost = ? AND srp = ?";<br />
<br />
OleDbCommand cmd = new OleDbCommand(sql, cn);<br />
<br />
OleDbParameterCollection pc = cmd.Parameters;<br />
OleDbParameter param;<br />
param = pc.Add("ProductID", OleDbType.Integer, 0, "prouctID");<br />
param.SourceVersion = DataRowVersion.Original;<br />
param = pc.Add("Description", OleDbType.VarChar, 50, "description");<br />
param.SourceVersion = DataRowVersion.Original;<br />
param = pc.Add("Cost", OleDbType.Currency, 0, "cost");<br />
param.SourceVersion = DataRowVersion.Original;<br />
param = pc.Add("SRP", OleDbType.Currency, 0, "srp");<br />
param.SourceVersion = DataRowVersion.Original;<br />
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swarm wrote:
param = pc.Add("ProductID", OleDbType.Integer, 0, "prouctID");
Could it be that the last parameter to Add should be 'productID'?
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I'm not sure about that but I thought that the order of the parameters in the parameterCollection should reflect to the order on the SQL statement. I do not find the rationale of adding the product id parameter last. I will try your suggestion though. Thanks
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That wasn't what I was trying to say. The parameters in the collection must be in the same order as in the statement, for OleDbCommand.
I was assuming that you'd copied and pasted your code when making your post. There are a number of typos or, at least, inconsistencies between the statement, the parameter names, and the column names.
Specifically, in the SQL statement you have 'desription' but in the column name and parameter name you have 'description', and also you have 'productID' in SQL, but the column name parameter has 'prouctID'.
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Thank you so much and I'm so sorry for the confusion. I should have perused my codes carefully. There were indeed typos.
Cheers
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Dear friends,
I am new to databases and have many questions swinging in my head. The main question is related to the concurrency and consistency issue.
In .NET, Oracle, and Access client server systems, how the DB system manage the different copies of same data to different users. Suppose a client opens a record set to perform some operation on it and write results back in the database. At the same time some other client updates the same rows, then how error is detected and handled by first client. How much control as such do we have and how pure is the object orientation ?
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Try searching the MSDN website for "optimistic locking".
On the system I have just developed, we have a "VersionNo" column. Whenever we retreive a resultset that may be modified by the user, we include this column in the column-list.
When we update the SQL-Server database we use stored-procedures that contain:
UPDATE SomeTable SET
SomeColumn = @SomeValue,
VersionNo = CASE WHEN VersionNo > 32000 THEN 1 ELSE VersionNo + 1 END,
LastUpdateUser = @UserId,
LastUpdateDate = GetDate()
WHERE SomeKeyColumn = @SomeKeyValue
AND VersionNo = @OriginalVersionNo
SELECT @intError = @@ERROR, @intRowCount = @@ROWCOUNT
IF @intRowCount <> 1 BEGIN
RAISERROR('Concurrency problem - someone else has updated record', 16, 1)
RETURN 1
ENDThis "VersionNo" value is incremented each time that we update the database. If the number of rows updated (@intRowCount) is not one then someone else has updated your record after you selected it. The case-statement stops the version-number from exceeding the size of the field (smallint in this case).
You can use similar code for Oracle and MS-Access databases - and you don't need to be using stored procedures (although it means that your concurrency control is isolated in a single place in your code).
Hope this helps.
Andy
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There's also the SQL Server ROWVERSION datatype, which SQL Server automatically updates whenever the row is changed. However, IIRC, it doesn't write a predictable sequence number, so if you need it to show versions 1, 2, 3, etc in sequence, you'll have to do it as above.
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I'm having a problem with when (or even if) the DataRowState of DataRows are getting changed. Here's the situation:
I have one main table which is bound to a form which displays one record from the main table. If you make changes to the form and then try and update the database, nothing happens. If you move to another record and then try it, it works. I've determined that this is because even though the DataRow has a Proposed version set (HasVersion(DataRowVersion.Proposed)) returns true, the DataRowState is still Unchanged until you move to another record. Does anybody know why this is and if I can change the DataRowState myself?
This situation is a fairly minor problem by itself, but it becomes a major problem because I also have a child table linked to the main table and that never gets changed to DataRowState.Modified so I can never update it.
Please help!!!
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Can you post the codes for the update?
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