I have data being processed by an app which needs to sort the data based on whether or not a bit is flipped. The tables are identical. The code as it stands looks something like this:
DataTable dt2 = dt1.Clone();
DataRow r = dt1.NewRow();
FillUp(ref r);
if(bitISetEarlier)
dt2.ImportRow(r);
else
dt1.ImportRow(r);
Now, a clear problem I was having is that if the row wasn't already attached to a table, ImportRow() fails silently and I end up with an empty table. When I changed this to:
if(bitISetEarlier)
dt2.Rows.Add(r);
else
dt1.Rows.Add(r);
I started getting an exception saying that a function was trying to add a row that existed for another table. So when I tried this:
if(bitISetEarlier)
if(r.RowState == DataRowState.Detached)
dt2.Rows.Add(r)
else dt2.ImportRow(r);
else
if(r.RowState == DataRowState.Detached)
dt1.Rows.Add(r)
else dt1.ImportRow(r);
the exception stopped, but any attempt to assign to dt2 still states that the row belongs to another table, but if I comment out the dt2 if statement and just attempt ImportRow(), the dt2.Rows.Count remains at 0 and no records assigned.
I need to populate the DataRow before knowing which table it belongs in, but I have no idea what columns the row will have before it hits this function. The condition that indicates which table it should go to is not stored with the data in the DataTable.
Is the problem that even though they have identical columns, NewRow() is adding an attribute to the row that makes it incompatible with the sister table? Is there a way I can get the same functionality as NewRow() (copy schema without knowing what any of the columns are ahead of time) but that I can dynamically assign? I'm aware I could probably manually construct a row that is compatible with either by wrapping it in a for loop and building out the columns every time i need the new row using the DataTable.Columns property, but I'd like to avoid doing that if possible.
I found my solution. Since I can't add the row built off of one table to the other table directly, I figured it was the DataRow object that was problematic, but the ItemArray property was probably all I needed.
if (isErrorRow)
{
//nr is the NewRow for dt1
var nr2 = dt2.NewRow();
nr2.ItemArray = nr.ItemArray;
dt2.Rows.Add(nr2);
}
This effectively cloned the rows.
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 hoping you guys can help me figure out why this is happening. I've been tearing my hair out trying to figure this out.
Here's an example directly from my code (with the boring bits cut out)
...(Set up the connection and command, initialize a datatable "dataTable")...
using (SqlDataReader reader = cmd.ExecuteReader())
{
//Query storage object
object[] buffer = new object[reader.FieldCount];
//Set the datatable schema to the schema from the query
dataTable = reader.GetSchemaTable();
//Read the query
while (reader.Read())
{
reader.GetValues(buffer);
dataTable.Rows.Add(buffer);
}
}
The error is
Input string was not in a correct format.Couldn't store in NumericScale Column. Expected type is Int16.
The specific column data types as returned by the schema are (ordered by column)
System.Data.SqlTypes.SqlInt32
System.Data.SqlTypes.SqlInt32
System.Data.SqlTypes.SqlByte
System.Data.SqlTypes.SqlMoney
System.Data.SqlTypes.SqlString
System.Data.SqlTypes.SqlGuid
System.Data.SqlTypes.SqlDateTime
It would appear that the data that should be in column #5 is actually appearing in column #3. But that is pure speculation.
What I know is that in order to use a dataTable "dynamically" with a query that can continue any number of different types of data the best route is to use GetSchemaTable() to retrieve it.
What I Saw In The Debugger
When I dropped into the debugger I took a look at dataTable's types built from the schema vs. the types returned to the object from reader.GetValues(). They are exactly the same.
It seems like dataTable.Rows.Add(buffer) is adding the columns a few columns off from where it should be. But this shouldn't be possible. Especially with the schema being directly built from the reader. I've played with options such as "CommandBehavior.KeyInfo" within ExecuteReader() and still had the same error occur.
Note: I need to run the query this way to enable the end-user to halt the query mid-read. Please do not suggest I scrap this and use an SqlDataAdapter or DataTable.Load() solution.
I'd really appreciate any help. Thank you!
Method DbDataReader.GetSchemaTable() return metadata table containing column names and types. It is not an empty table that one could expect. For more details see MSDN
I'm sorry but GetSchemaTable retrieves schema for a given table and GetValues retrieves the actual row data. E.g. your dataTable will contain columns like column name, column type, etc. (see MSDN reference) while your buffer will contain the actual data whose representation will differ from what the dataTable contains.
Why don't you just use:
dataTable.Fill();
Why are you manually loading it one row at a time?
Please check what you are inserting into the column row which gas GUID data type. I got the same error and found that while inserting records after reading records from csv file, there were couple of empty spaces in csv file.
DataRow contains a Table property, which seems to return the entire Table for which this row belongs.
I'd like to know if I can use that table safely, or if there are gotcha's.
In http://msdn.microsoft.com/en-us/library/system.data.datarow.table.aspx documentation, it says "A DataRow does not necessarily belong to any table's collection of rows. This behavior occurs when the DataRow has been created but not added to the DataRowCollection.", but I know for a fact my row belongs to a table.
In terms of pointers, if each Row from DataTable points to original DataTable, than I'm good to go. Is that all 'Table' property does?
Just to explain why I'm trying to get entire Table based on a single DataRow:
I'm using linq to join two (sometimes more) tables. I'd like to have a generic routine which takes the output of linq (var), and generate a single DataTable with all results.
I had opened another question at stackoverflow (Join in LINQ that avoids explicitly naming properties in "new {}"?), but so far there doesn't seem to be a generic solution, so I'm trying to write one.
if you know the row is part of table than yes you can access it without any problem. if the possibility exists where the row may not be associated to a table than check if the property is null.
if(row.Table == null)
{
}
else
{
}
As long as it's not null, you can use it freely.
I have two datatables one has few rows other is empty.
I am running a loop over first one to copy some of the rows to another table.
I am getting error 'The row already belongs to another table'.
Is there any way to copy DataRows one by one to other DataTable.
thanks in advance
Use
newtable.ImportRow(oldtable.Rows[i])
where i is the desired row number.
as explained in http://support.microsoft.com/kb/308909/en-us
copy the ItemArray, of course just works when the columns are the same
var dtCopyTo = new DataTable();
foreach(var rowCopyFrom in dtCopyFrom.Rows)
{
var updatedDataRow = dtCopyTo.NewRow();
updatedDataRow.ItemArray = rowCopyFrom.ItemArray;
dtCopyTo.AddRow(updatedDataRow);
}
ps: code is typed without ide so check syntax pls