Loop Question

[SIMIN]

Hello,

I use this code to loop through all items and read all of them, from 1st item to the last one!

Dim ReadUsers As New OleDb.OleDbCommand("SELECT * FROM Emails WHERE GroupID = '" + MyID + "'" + SortSQL, MyConnections)
Dim MyReader1 As OleDbDataReader = ReadUsers.ExecuteReader
While MyReader1.Read
   ...
End While

This is OK when I want to read all items of this table.

But what should I do if I want to read only item number 100 to 200?

I mean in the above code how can I change the While loop to a For loop with specified start and end point?

Thank you for helping :)

[PlausiblyDamp]

DataReaders are designed to be accessed in a sequential manner, there is no way to skip to a certain row without reading all the rows before it.

 

Personally I would change the select statement to just bring back the rows I am interested in rather than all rows. You might alslo want to look at parameterising the query as building a string that way can open you up to security risks.

[SIMIN]

Thanks, you know there's a problem, my real database has around 10.000 records.

When I want to read all of records, there's no problem.

But for example, if I want to read the last 1000 records, from 9001 to 10.000, there will be a long delay if I want to read the firs 9.000 records and just skip them / continue while...

What other way do you recommend?

[PlausiblyDamp]

Do the records have a sequential identifier or similar? How would you normally identify which record you want to start at?

[SIMIN]

User specify that for example he wants to read from record #1 to #100

OR from #1000 to #1500

[PlausiblyDamp]

Do these numbers match up with a particular field or would they simply be based on the data returned?

 

Out of interest what database are you using?