在事务中使用SQL“选择”填充数据表

Question

I would like to fill a datatable with results from a SQL select statment but using a transaction. The reason that I am using a transaction is because I have a list of names (as a datatable), and I want to iterate through the list of names and select the database rows where the name = the name on the list. There are 500,000 names in the database and I only want to retreive the relevant rows. I have the code for the procedure as I think it should look like (untested) BUT I dont know HOW to place the data into a datatable .... so Im missing something where I declare the datatable and the 'fill' of that table , could someone help with this ? Or suggest how else I can get the information out of the batabase without looking up each name individually.

 Using connection As New SQLite.SQLiteConnection(R2WconectionString)
            connection.Open()
            Dim sqliteTran As SQLite.SQLiteTransaction = connection.BeginTransaction()
            Try
                oMainQueryR = "SELECT NameID, Address, Ocupation FROM Employees Where Name= :Name"
                Dim cmdSQLite As SQLite.SQLiteCommand = connection.CreateCommand()
                With cmdSQLite
                    .CommandType = CommandType.Text
                    .CommandText = oMainQueryR
                    .Parameters.Add(":Name", SqlDbType.VarChar)
                End With
               'Prevent duplicate selects by using a dictionary
                Dim NameInalready As New Dictionary(Of String, String) 

                For Each row As DataRow In TheLIST.Rows
                    If NameInalready.ContainsKey(row.Item("Name")) Then
                    Else
                        NameInalready.Add(row.Item("Name"), "")
                        cmdSQLite.Parameters(":Name").Value = row.Item("Name")
                        cmdSQLite.ExecuteNonQuery()
                    End If

                Next

                sqliteTran.Commit()

            Catch ex As Exception
            End Try
        End Using

Answer 1

First, you don't need a transaction because you aren't updating the database.

Second, depending on the possible number of Names in TheLIST, it might be worthwhile for you to change the name selector to IN (ie SELECT * FROM Employees WHERE Name IN ('name1', 'name2') . However, if you expect more than about 10, this is probably not worth trouble.

Finally, you need to create a new DataTable to hold the results. Then you need to create a DataAdapter passing cmdSqlLite as the constructor parameter. And finally, replace your ExecuteNonQuery with DataAdapter.Fill(DataTable).

For example (after Dim cmdSQLite ):

Dim oDataTable As New DataTable("Employees")
Dim oAdapter As New SqliteDataAdapter(cmdSQLite)

and replacing the ExecuteNonQuery line with:

oAdapter.Fill(oDataTable)

I will qualify this code by saying it may need some tweaks. I only work with class objects and collections, so my preference would have actually been to load a collection of Employee class instances.

I would have done that by replacing ExecuteNonQuery with ExecuteReader and then the loading the read data into a new class instance. This type of approach resolves various issues with serializing the data across service boundaries (ie Xml for web services) and also lets you embed business logic, if needed, into the classes.