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Sorry I didn't reply sooner -- I was hoping you'd say "web forms" -- in which case the answer is that databinding in web forms doesn't trigger any methods that tell you if the data changed or allow automatic updating of a dataset. I'm afraid I haven't spent enough time on windows form design and data binding to help much here.
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Greetings my dear fellow programmers,
I have a situation!
I need to create a ADODB Stream object in VC++.
How can i do it?
Nuno Henrique Mendes
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I have Master-Detail datagrid. The detail datagrid is embedded in the Master datagrid. In the detail datagrid I want to implement paging ,sorting etc. I have addes the event handlers delegates manually. For some reason the pageindexchanged or sort events for the detail datagrid. Does anyone know of this behaviour? I saw a lot Master-Details datagrids on the internet, nobody seems to have implemented paging-sorting for details grid embedded within a datagrid. thanks
Madhuri Mittal
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Hiya can someone please give me a working example of connecting to an SQL database using ADO and accessing the contents.
I tried tried it myself but I keep getting a system error.
Thanks a million.
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How are you trying to connect? through an ASP.NET page, through a VBA Application.
Please post your code if the site permits that, I'm not sure.
grahamoj wrote:
connecting to an SQL database using ADO and accessing the contents
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To tell you the truth not too sure. Only learning ADO a few days but already it is driving me mad connecting to the SQL server I have.
Here is my code:
try
{
HRESULT hResult;
if(FAILED(::CoInitialize(NULL)))
return;
_ConnectionPtr pConnection;
hResult = pConnection.CreateInstance(__uuidof(Connection));
hResult = pConnection->Open(_T("Provider=SQLOLEDB.1; Data Source=(local);Initial Catalog=Branch;Trusted_Connection=yes;"),
_T(""),
_T(""),
adOpenUnspecified);
}
catch(_com_error &e)
{
_bstr_t bstrSource(e.Source());
_bstr_t bs = _bstr_t(" Error: ") + _bstr_t(e.Error()) + _bstr_t(" Msg: ")
+ _bstr_t(e.ErrorMessage()) + _bstr_t(" Description: ")
+ _bstr_t(e.Description());
MessageBox(0,bs,bstrSource, MB_OK);
}
I didn't think I needed to login once I used the Trusted Connection=yes. could you plz have a quick look and tell me what I am doing wrong. Once I can get the connection, I should be ok.
Oh and Branch is the name of my database.
Thanks.
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http://www.connectionstrings.com/
Go to this URL for all different SQl Connection Strings.
HTH
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hey this is question for DB specially SQL Server experts
i have 2 quetions.
1) i have a field in table which is of 215 bytes. i have about 1.1 Million records in my table. I noticed that only 20,000 records of these 1.1 Million records require more than 50 Bytes for that field. Now if partition my table in two so that one table has field length of 50 while other has of 215, will there be any performance gain in terms of speed and memory? i am not talking in terms of normalization ( just performance) and how much do u think will be performance gain if any?
2) After any qury on SQL server, its memory usage goes to its maximum allowed memory usage ( my minimum is 0), but when query has ended memory usage still remains the same. is there any way to overcome this problem?
Thanx in advance!!
Shoaib
Muhammad Shoaib Khan
http://geocities.com/lansolution
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M.Shoaib Khan wrote:
Now if partition my table in two so that one table has field length of 50 while other has of 215, will there be any performance gain in terms of speed and memory?
Shoaib,
This is! a method of normalization as far as I can see.
And the answer is yes, you would boost the performance level of your queries if you were to do the above.
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I obviously haven't been using ADO very long, but I'm sure there's a better way to accomplish this. I have a table to maintain - a list of committee names and chairpersons sorted by year served called, oddly enough, Chairs. I want to display them and allow selection of one record for editing. The table contains only the index of the matching entry in another table for the committee names (Comms) and chairpersons (People). The brute force method I'm attempting now chugs through the records in Chairs for each year, extracts the index for each person and committee, then performs individual queries to retrieve text data from the Comms and People tables for display on a web page. That seems like an awful lot of queries to perform such a simple task. Is there a smarter way to do this that doesn't require so many trips back to the database?
[EDIT] It's an Access DB because of various limitations - SQL Server and MySQL are not available - so I'm limited in what tools are usable. [/EDIT]
"Ask not for whom the bell tolls;
It tolls for thee..."
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Its sounds like you are on the right track, with a normalize table(Chairs). Why not just preform the join to the other two tables? Like such: SELECT {WHATEVER} FROM Chairs as c, Comms as Com, People as p WHERE c.FK_PeopleID = p.PK_peopleID AND c.FK_CommsID = com.PK_CommsID AND [Whatever time constraints for the chairs table here]
Although this SQL may not be the answer your are looking for, I think that given your boggle the best solution is a one sql solution, which will then require only a sigle trip to Access.
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That's the approach I was looking for, but I haven't used a JOIN before. I usually let Access do it, and don't know how the SQL should be structured. I really need a decent SQL reference! Thanks for the idea!
"Ask not for whom the bell tolls;
It tolls for thee..."
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When I input my first entry in a dataset with an autoincrement field, it starts at 0. When I do the same thing in MySQL, it starts at 1. How do I reconcile the difference?
Thanks
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I am having trouble getting table constraints to work the way I think they should. I have unique constraints set up for two fields of a three field table, and when I add a row to the table, I was hoping the constraints would be honored at that time. I want the new row to have unique values in the fields for the entire column in the table. Here is what I am setting up:
private OdbcDataAdapter keyvalueDA;
.
.
.
keyvalueDA = new OdbcDataAdapter
("SELECT value_id, value, valuehash FROM keyvalue", conn);
keyvalueDACmdBuilder = new OdbcCommandBuilder(keyvalueDA);
keyvalueDA.FillSchema(ds, SchemaType.Source, "keyvalue" );
.
.
keyvalueDA.Fill(ds, "keyvalue");
.
.
.
// Now in a method, I insert the new values in the table.
DataTable myTable = ds.Tables[tableName];
myDataRow = myTable.NewRow();
myDataRow["value"] = valuepassedin1;
myDataRow["valuehash"] = valuepassedin2;
// and then call
myTable.Rows.Add(myDataRow);
At this point I would expect since valuehash is set to be unique, that if I tried to enter a duplicate, it would complain here.
It does not.
I get no indication of a problem until I try to update the dataset into the real database
keyvalueDA.Update(ds, "keyvalue");
which then throws an exception, duplicate key entry.
When I look at the dataset, it shows that the unique constraints are being enforced
in dataset:
enforceConstraints true bool
Do I need to explicitly set the constraints for the "new row" before I add it to the table?
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Okay, the problem was in how the database was setup which I was getting the schema out of. The database had a table with three fields and had declared two of the fields to be primary keys. The unique constraint can only be applied to "THE" primary key. Once I removed the other primary key, the constraint worked.
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If I create a stored procedure that uses a temporary table, I cannot get a .NET data adapter to configure correctly for that stored procedure. A workaround is to create a stored procedure with the same data columns, generate a data adapter and dataset, then change the stored procedure called by the data adapter. Is there a better solution to this problem?
Thanx...
>>>-----> MikeO
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I am getting the following error when I call my dataTable.Update(dataset, tablename) method.
Microsoft.Data.Odbc.OdbcException: ERROR [07002][MySQL][ODBC 3.51 Driver][mysqld-4.0.12-nt]SQLBindParameter not used for all parameters
As this is a bulk update using a dataset, I am at a loss as to figure out which entry is causing the problem. Any troubleshooting tips?
Thanks.
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The following SQL statement returns a recordset if I run it in query analyzer, but it returns NO recordset if I call it from ASP (i.e. via ADO):
insert into module_hyperlinks_all<br />
(definitionid, pageid, linktype, url, innerhtml, target, styleid)<br />
values<br />
(18,0,0,'http%3A///','link1','',0)<br />
select @@identity as yay
If anyone can explain to me why this statement doesn't return a recordset (i.e. there isn't even a recordset with no rows returned, it's simply a closed, uninitialised object) when I execute it from ASP, I would be extremely grateful! (SQL Server 7)
The ASP error when I try to do anything with the recordset is:
ADODB.Recordset error '800a0e78' <br />
<br />
The operation requested by the application is not allowed if the object is closed.
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The reason is that the insert returns a completion marker. ADO is not smart enough to skip over to the first result set based return code.
To get around this, wrap the whole set up in a stored procedure and only the results will be returned. Don't forget to put SET NOCOUNT ON as the first line of your stored procedure.
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Cool, that fixed it, thanks!
NATHAN RIDLEY
Web Application Developer
generalgherkin@yahoo.com
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I am trying to search through a dataset dataTable to find a value based on a search string. I am using the DataTable.Select method but I am having trouble with the search string when it contains the single quote character.
I have tried escaping the single quote with a "\", but I still get errors.
How do you escape special characters in the select string when using the DataTable.Select method?
public string ReturnId(string tableName, string field, string searchValue)
{
// query table return DataRow
// searchValue must be Escaped for SQL special chars.
// this will return -1 for not found
//http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdatadatatableclassselecttopic2.asp
string idFound = "-1";
DataTable myTable = ds.Tables[ tableName ];
string strExpr;
// strings must be enclosed in single quotes for these expressions
// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdatadatacolumnclassexpressiontopic.asp
strExpr = field + " = '" + searchValue +"'";
DataRow[] foundRows;
// Use the Select method to find all rows matching the filter.
// In this app, these best be unique
try
{
foundRows = myTable.Select(strExpr);
if ( foundRows.Length != 0 )
{
switch (tableName)
{
case "asset":
idFound = (foundRows[0]["asset_id"]).ToString(); // row 0, column 0 asset_id
break;
case "keyvalue":
idFound = (foundRows[0]["value_id"]).ToString(); // row 0, column 0 value_id
break;
case "filevalue":
idFound = (foundRows[0]["value_id"]).ToString(); // row 0, column 0 value_id
break;
}
}
}
catch(Exception err)
{
MessageBox.Show(err.ToString() + "\r\n" +strExpr.ToString());
}
return idFound;
}
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Try replacing all of the single-quote characters in searchValue are replaced by two single-quotes. So your final select expression for "O'Leary" becomes:
myFieldName = 'O''Leary'
Hope this works for you.
Andy
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Thanks for the quick and accurate suggestion. That did the trick.
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Hi,
I am creating a table using ADOX, in VC++ dynamically. And creating fileds in the table, but i am not able to create MEMO fields with zero length and not required attributes.
Can someone help me out on this one.
Mayank Goyal
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Hi..
I have a table that i want to make some updates , inserts to it..
the new values are read form an XML file (which contains the new valuse)..like this:
rs.Open "Update.xml", , adOpenStatic, adLockReadOnly, adCmdFile
now I want a direct way to update existing fields and insert the new ones..
I can make a loop .. search for each existing record by ID , update it.. And if not found
I insert it ,, but this is not fast, smart enough, any suggestions ?
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