I'm trying to populate a DataTable, to build a LocalReport, using the following:
MySqlCommand cmd = new MySqlCommand();
cmd.Connection = new MySqlConnection(Properties.Settings.Default.dbConnectionString);
cmd.CommandType = CommandType.Text;
cmd.CommandText = "SELECT ... LEFT JOIN ... WHERE ..."; /* query snipped */
// prepare data
dataTable.Clear();
cn.Open();
// fill datatable
dt.Load(cmd.ExecuteReader());
// fill report
rds = new ReportDataSource("InvoicesDataSet_InvoiceTable",dt);
reportViewerLocal.LocalReport.DataSources.Clear();
reportViewerLocal.LocalReport.DataSources.Add(rds);
At one point I noticed that the report was incomplete and it was missing one record. I've changed a few conditions so that the query would return exactly two rows and... surprise: The report shows only one row instead of two. I've tried to debug it to find where the problem is and I got stuck at
dt.Load(cmd.ExecuteReader());
When I've noticed that the DataReader contains two records but the DataTable contains only one. By accident, I've added an ORDER BY clause to the query and noticed that this time the report showed correctly.
Apparently, the DataReader contains two rows but the DataTable only reads both of them if the SQL query string contains an ORDER BY (otherwise it only reads the last one). Can anyone explain why this is happening and how it can be fixed?
Edit:
When I first posted the question, I said it was skipping the first row; later I realized that it actually only read the last row and I've edited the text accordingly (at that time all the records were grouped in two rows and it appeared to skip the first when it actually only showed the last). This may be caused by the fact that it didn't have a unique identifier by which to distinguish between the rows returned by MySQL so adding the ORDER BY statement caused it to create a unique identifier for each row.
This is just a theory and I have nothing to support it, but all my tests seem to lead to the same result.
After fiddling around quite a bit I found that the DataTable.Load method expects a primary key column in the underlying data. If you read the documentation carefully, this becomes obvious, although it is not stated very explicitly.
If you have a column named "id" it seems to use that (which fixed it for me). Otherwise, it just seems to use the first column, whether it is unique or not, and overwrites rows with the same value in that column as they are being read. If you don't have a column named "id" and your first column isn't unique, I'd suggest trying to explicitly set the primary key column(s) of the datatable before loading the datareader.
Just in case anyone is having a similar problem as canceriens, I was using If DataReader.Read ... instead of If DataReader.HasRows to check existence before calling dt.load(DataReader) Doh!
I had same issue. I took hint from your blog and put up the ORDER BY clause in the query so that they could form together the unique key for all the records returned by query. It solved the problem. Kinda weird.
Don't use
dr.Read()
Because It moves the pointer to the next row.
Remove this line hope it will work.
Had the same issue. It is because the primary key on all the rows is the same. It's probably what's being used to key the results, and therefore it's just overwriting the same row over and over again.
Datatables.Load points to the fill method to understand how it works. This page states that it is primary key aware. Since primary keys can only occur once and are used as the keys for the row ...
"The Fill operation then adds the rows to destination DataTable objects in the DataSet, creating the DataTable objects if they do not already exist. When creating DataTable objects, the Fill operation normally creates only column name metadata. However, if the MissingSchemaAction property is set to AddWithKey, appropriate primary keys and constraints are also created." (http://msdn.microsoft.com/en-us/library/zxkb3c3d.aspx)
Came across this problem today.
Nothing in this thread fixed it unfortunately, but then I wrapped my SQL query in another SELECT statement and it work!
Eg:
SELECT * FROM (
SELECT ..... < YOUR NORMAL SQL STATEMENT HERE />
) allrecords
Strange....
Can you grab the actual query that is running from SQL profiler and try running it? It may not be what you expected.
Do you get the same result when using a SqlDataAdapter.Fill(dataTable)?
Have you tried different command behaviors on the reader? MSDN Docs
I know this is an old question, but for me the think that worked whilst querying an access database and noticing it was missing 1 row from query, was to change the following:-
if(dataset.read()) - Misses a row.
if(dataset.hasrows) - Missing row appears.
For anyone else that comes across this thread as I have, the answer regarding the DataTable being populated by a unique ID from MySql is correct.
However, if a table contains multiple unique IDs but only a single ID is returned from a MySql command (instead of receiving all Columns by using '*') then that DataTable will only organize by the single ID that was given and act as if a 'GROUP BY' was used in your query.
So in short, the DataReader will pull all records while the DataTable.Load() will only see the unique ID retrieved and use that to populate the DataTable thus skipping rows of information
Not sure why you're missing the row in the datatable, is it possible you need to close the reader? In any case, here is how I normally load reports and it works every time...
Dim deals As New DealsProvider()
Dim adapter As New ReportingDataTableAdapters.ReportDealsAdapter
Dim report As ReportingData.ReportDealsDataTable = deals.GetActiveDealsReport()
rptReports.LocalReport.DataSources.Add(New ReportDataSource("ActiveDeals_Data", report))
Curious to see if it still happens.
In my case neither ORDER BY, nor dt.AcceptChanges() is working. I dont know why is that problem for. I am having 50 records in database but it only shows 49 in the datatable. skipping first row, and if there is only one record in datareader it shows nothing at all.
what a bizzareeee.....
Have you tried calling dt.AcceptChanges() after the dt.Load(cmd.ExecuteReader()) call to see if that helps?
I know this is an old question, but I was experiencing the same problem and none of the workarounds mentioned here did help.
In my case, using an alias on the colum that is used as the PrimaryKey solved the issue.
So, instead of
SELECT a
, b
FROM table
I used
SELECT a as gurgleurp
, b
FROM table
and it worked.
I had the same problem.. do not used dataReader.Read() at all.. it will takes the pointer to the next row. Instead use directly datatable.load(dataReader).
Encountered the same problem, I have also tried selecting unique first column but the datatable still missing a row.
But selecting the first column(which is also unique) in group by solved the problem.
i.e
select uniqueData,.....
from mytable
group by uniqueData;
This solves the problem.
I'm having major problems trying to clear a DataTable in C#.
At all other points when editing information in the database, I've used something like
somethingTableTableAdapter1.Update(greenParksDataSet);
greenParksDataSet1.AcceptChanges();
and this has worked just fine. However, in one of my forms I have a button to clear the open table. It seems to clear the DataTable in memory, but not actually propagate the changes to the database. Essentially the code boils down to
greenParksDataSet.HistoryTable.RecieptIDColumn.AutoIncrementSeed = -1;
greenParksDataSet.HistoryTable.RecieptIDColumn.AutoIncrementSeed = -1;
greenParksDataSet.HistoryTable.RecieptIDColumn.AutoIncrementSeed = 1;
greenParksDataSet.HistoryTable.RecieptIDColumn.AutoIncrementSeed = 1;
greenParksDataSet.HistoryTable.Rows.Clear();
historyTableTableAdapter.Update(greenParksDataSet);
greenParksDataSet.AcceptChanges();
I've tried messing around with the order of things but nothing seems to work. With that code on its own, the DataTable is cleared (and the changes are shown in the DataGridView) but when adding a historyTableTableAdapter.Fill(greenParksDataSet.HistoryTable); after that, it is shown that the database is not being changed whatsoever.
I've probably missed something obvious, but I've been puzzling over this for ages, and any help would be appreciated. Thanks!
Have a look at this question/answer.
Clear just works on the datatable in memory - it does not flag them for deletion.
I think you are using a binding source so try this :
greenParksDataSet.HistoryTable.Rows.Clear();
HistoryTableBindingSource.EndEdit();
historyTableTableAdapter.Update(greenParksDataSet);
greenParksDataSet.AcceptChanges();
I've a WPF situation with one page that has a datagrid with clients, and another page with field to fill in a new client.
I want the "new-client-page" to search the highest clientID en increment that with 1 for the new client, this sounds very simple, but I've a problem with it.
In the table adapter of the table, I added a new query: SELECT MAX(clientID) FROM clients
I execute the query with:
DataSet1TableAdapters.klantenTableAdapter tableAdapter = new DataSet1TableAdapters.klantenTableAdapter();
DataSet1 datasetvar = new DataSet1();
int returnValue = (int)tableAdapter.GetMaxKlantnr();
This works fine once. I get the highest value in returnValue, but if I go for the second time to the "new-client-page", the clientID is still the same..
I tried to update the dataset with tableAdapter.Update(datasetvar); but that doesnt make sense.. :(
Lars what database are you using? Set the ID column as identity and it will be auto generated by the db, your solution would not support any concurrency anyway and it's not the way to go to read the max id and add 1 to it...
You need to set it when you add a new row. It is then executed as an INSERT by the adapter. Adapters commit only changes.
The code would look almost like:
var newRow = ClientTable.NewRow();
newRow["ClientID"] = GetNewID();
...set other fields...
ClientTable.Rows.Add(newRow);
Adapter.Update(ClientTable);
I´m trying to set a cell of type "System.Int32" in a DataSet by code, and my try looks like this:
int aCarID = 5; // as an example...
// points out the row that I want to manipulate - I guess this is what doesn´t work???
int insertIndex = myDataSet.tableCars.Rows.Count
myDataSet.tableCars.Rows[insertIndex]["CarID"] = aCarID;
What happens is: I get an exception of "System.IndexOutOfRangeException".
You´re allowed to say that I´m stupid as long as you provide an answer...
UPDATE!
Yes, I´m trying to create a new row, that´s true - that´s why I´m not using "-1".
So what´s the syntax to create a new row?
If I use tableCars.Rows.Add(...) I need to supply a "DataRow Row" to the Add-function, and I don´t have one to provide - yet! (Catch 22)
NEW UPDATE!
Ooops, found it - "NewRow()" :-)
You do realize that indices start with zero in C#? That means if your table has 3 rows, you're trying to access the 4th row because insertIndex = 3.
Try insertIndex - 1.
Edit: Since you're trying to add a new row and already found out how to do so, also don't forget to save those changes to the database (I assume that's what you want to do). The most simple way is to set the UpdateCommand-property of the DataAdapter you used to fill the DataSet (or actually the DataTable in the DataSet).
You can also have the update commands generated, using a subclass of the DbCommandBuilder.
This is a classic off-by-one: valid rows are at indices 0... Rows.Count -1
If you want to make a new row, call tableCars.AddNew() first.
From MSDN:
An IndexOutOfRangeException exception is thrown when an attempt is made to access an element of an array or collection with an index that is outside the bounds of the array or less than zero.
so the problem is when you use a wrong index as Christian said.
try to create new row first, because you want to access row which doesn't exists, or you have to insert your information into row indexed (insertIndex - 1).
Datarow indexes first position is 0, as in arrays.
You're using a strong-typed dataset, but your insert code is actually for a non-strongly typed dataset.
The following code will work for you (and is much easier!)
var insertRow = myDataSet.tableCars.NewtableCarsRow();
insertRow.CarID = aCarID;
myDataSet.AcceptChanges();
That's it!
NOTE: this code works from .NET version 3.5 onwards. For prior versions, replace the var keyword with tableCarsRow (I'm assuming that you didn't customize the default name for the datarow in the DataSet designer).
I perform a set of operations on a dataset table:
MyDataSet sharedDS = new MyDataSet();
MyDataSet referenceDS = new MyDataSet();
sharedDS.Table1.Reset();
sharedDS.Merge(referenceDS);
I get a System.ArgumentException: Column_X does not exist in Table1 if I try to access the column this way:
MyDataSet.Table1.FindByKey().Column_X
However, this way everything's fine:
MyDataSet.Table1.FindByKey()["Column_X"]
Can anyone explain what's the issue here?
Reference (originally meant for another problem): Reset primary key
I think this line :
sharedDS.Table1.Reset();
is causing you trouble.
I think the .reset is clearing the schema. Use .Clear() istead!