I am facing the following issue: I have an composite index on a database index1 {binaryColumn1, binaryColumn2}. I am using the following to set the index to use:
Api.JetSetCurrentIndex(_session, _table, index1);
to create the key:
Api.MakeKey(_session, _table, binaryValue, MakeKeyGrbit.NewKey);
and than try to perform the search with:
Api.TrySeek(_session, _table, SeekGrbit.SeekEQ);
This works and seek returns true correctly if index1 is only for 1 column. If I have multiple columns and try to search the value for a single column (ex. for binaryColumn1 = {0x01, 0x23}) it always returns false.
How can I search for this one value? (ps. I cannot change the index nor create new ones.) Is this possible?
Thank you
What you did would only work for {0x01, 0x00}. You can't do it with a single call, because the value of the second column will be mixing up the SeekEQ grbit.
You could do a SeekGE, but then you'll need to retrieve the column to make sure the value is actually correct (and not something like {0x22, 0x23}). You'll have to do something like:
SetCurrentIndex()
MakeKey( ..., binaryValue1, MakeKeyGrbit.NewKey | MakeKeyGrbit.FullColumnStartLimit); // Appends the rest of the search buffer with 0x00's.
Seek(GE);
MakeKey(... binaryValue1, MakeKeyGrbit.NewKey | MakeKeyGrbit.FullColumnEndLimit); // Appends the rest of the search buffer with 0xff's.
Api.JetSetIndexRange();
Then you can use Api.TryMoveNext() to iterate through all rows that have that column equal to binaryValue1.
Also look at the test code included with the project -- the HowDoI.cs file has lots of good examples.
Sorry for the pseudo-code; I don't have the source code handy at the moment.
-martin
I am trying to reset the number of columns in an Excel ListObject. I know you can add and remove columns one-by-one, but I want to avoid unnecessary loops. I instead decided to resize the ListObject using the Resize method.
Here is the code that I am using (where OutputCasesTable is the ListObject):
OutputCasesTable.DataBodyRange.Value2 = "";
OutputCasesTable.Resize(OutputCasesTable.Range.Resize[ColumnSize: CaseCount]);
OutputCasesTable.DataBodyRange.Value2 = OutputCasesAray;
The above lines of code appear to work perfectly, however if the ListObject only contains 1 row of data, the DataBodyRange of the ListObject becomes null on the second line - producing an error when I try to change its cell's value. The row in excel still appears to be present.
The MSDN documentation says the following:
"The header must remain in the same row and the resulting list must overlap the original list. The list must contain a header row and at least one row of data."
Now I understand that "one row of data" implies that the row contains values - so the cause of the error here must be that the DataBodyRange cells all contain no value (""). However, a table with two data rows containing "" still doesn't have a row with data, does it?
I know there are many ways of accomplishing this task, but I want to understand why this happens.
Temporary Solution:
Replaced the code to only set the values to empty strings in columns that will be removed (columns above the new column count). All other columns will be replaced:
if(OutputCasesTable.ListColumns.Count - CaseCount > 0)
OutputCasesTable.DataBodyRange.Offset[ColumnOffset: CaseCount].Resize[ColumnSize: OutputCasesTable.ListColumns.Count - CaseCount].Value2 = "";
OutputCasesTable.Resize(OutputCasesTable.Range.Resize[ColumnSize: CaseCount]);
OutputCasesTable.DataBodyRange.Value2 = OutputCasesAray;
Personally I prefer looking at the first solution!
Is there anything I can do make it work with empty strings? Or do you have a better solution?
Best regards,
The Resize operation is the piece that kills the DataBodyRange, and clearly there's some internal logic that Resize uses, along the lines of "if there is only one row, and all the cells are empty, remove all the data rows. If there is more than one row, don't remove any".
I agree that this logic is a bit confounding. If your question is why did Microsoft implement it this way, I'd argue that although it's inconsistent, it's perhaps tidier in a way - it appears to the model that you're working with an empty table, and there's no way for the model to tell the difference graphically (it's not possible for a table to just have a header row).
When Resize turns up to do its work and finds a single-row blank table, it can't tell whether you have a zero-row table or a single-row table with empty strings. If it arrives and finds two empty rows, that's unambiguous (they must be meaningful rows).
For the workaround portion of your question, I'd suggest a tidier solution of just checking the ListRows.Count property, and adding one if necessary. Note that you can also use Clear instead of setting Value2 to blank; for me it reads as more self-explanatory.
OutputCasesTable.DataBodyRange.Clear();
OutputCasesTable.Resize(OutputCasesTable.Range.Resize[ColumnSize: CaseCount]);
if (OutputCasesTable.ListRows.Count == 0) OutputCasesTable.ListRows.Add();
OutputCasesTable.DataBodyRange.Value2 = OutputCasesAray;
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 am trying to get the index of the last used row in a spreadsheet. I've found that in excel it could be done like that:
int lastUsedRow = worksheet.Cells.SpecialCells(Excel.XlCellType.xlCellTypeLastCell,
Type.Missing).Row;
But this doesn't seem to work with GemBox. The idea is that I have a template excel file that I want to fill with more information and therefore need the last row, so that I can continue on the next one.
Hi you can just use ExcelFile.Rows.Count property.
Gets the number of currently allocated elements (dynamically changes when worksheet is modified)
Try the following:
int lastUsedRow = worksheet.Rows.Count - 1;
Also regarding the shahkalpesh suggestion, yes you can also achieve your task with that approach as well, here is how:
var usedRange = worksheet.GetUsedCellRange(true);
int lastUsedRow = usedRange.LastRowIndex;
Note: I haven't used Gembox. My answer is based on searching in the documentation.
GetUsedCellRange returns a CellRange, which has a property named LastRowIndex.
Does this work the same way as Excel?
I know how to make new columns, I know how to add a header to that column, but I am a little unsure about adding values programatically.
I am going to be looping through rows and then adding values to the new columns that I create based on some functions I perform on the Data Set. I thought a good way to start would be to just pick a row and loop through it and print out all the information in that row. If I could figure out how to do that, I could probably right all the code necessary to loop through appropriate rows and get the data I need. But I am a little confused about how to use this Range object...
Range rng = (Range)wkSheet.get_Range("A1", Type.Missing);
Lets say I wanted to print out all the Range Row information to a console? How would I loop through that Range and print out that information? Even change the information in the Range. I know how to change the value of a single row, the header, but changing multiple rows is alluding me.
object[,] values = (object[,])rng.Value;
Probably duplicate reading-from-excel