███小弟是个初学VB.Net的人,想对连数据库说几句███
拿棵草 2003-08-20 04:48:15 小弟是个初学VB.Net的人。这几天主要研究了一下数据库的连接。
以下是小弟对VB.Net中连接数据库的方法的理解,不知道对不对,请高手赐教!
1、一定要有一个OleDBDataAdapter对象;
2、也一定要有一个DataSet对象;
3、OleDBConnection对象可以没有。
因为连接时,可以这样:
Dim searchcmd = New OleDb.OleDbDataAdapter("select * from biao1", "Provider = Microsoft.Jet.OLEDB.4.0;data source= c:\a.mdb")
这样,就省去了定义OleDBConnection对象
以下,是小弟连接ACCESS,SQL SERVER,VFP数据库,并把数据库结果显示在DATAGRID中的代码:
'连SQL Server 2000
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim ds As New DataSet()
Dim con As New SqlClient.SqlConnection("server=c123;uid=sa;pwd=;database=northwind")
Dim daEmp As New SqlClient.SqlDataAdapter("Select * From Employees", con)
daEmp.Fill(ds, "Employees") '?如果你连接的是一张表的话,你可以:daEmp.Fill(ds)
DataGrid1.DataSource = ds
DataGrid1.DataMember = "Employees"
End Sub
'连接DBF数据库(需要安装MDAC2.7以上以及ODBC.NET)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim sConnectionString As String = "Driver={Microsoft Visual FoxPro Driver};SourceType=DBF;SourceDB=C:\HHLIB;Exclusive=No;"
Dim objConn As New Microsoft.Data.Odbc.OdbcConnection(sConnectionString)
Dim ds As New DataSet()
objConn.Open()
Dim da As New Microsoft.Data.Odbc.OdbcDataAdapter("Select * From cc", objConn)
da.Fill(ds, "cc")
DataGrid1.DataSource = ds
DataGrid1.DataMember = "cc"
objConn.Close()
End Sub
'连ACCESS
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim searchSQLStr As String
Dim ds As New DataSet()
Dim searchcmd = New OleDb.OleDbDataAdapter("select * from biao1", "Provider = Microsoft.Jet.OLEDB.4.0;data source= c:\a.mdb")
searchcmd.Fill(ds, "biao1")
DataGrid1.DataSource = ds
DataGrid1.DataMember = "biao1"
Dim temp As String
temp = ds.Tables("biao1").Rows(5)!fld2
Debug.Write(temp)
End Sub
有一些不明白的地方:
1、OleDBCommand这个对象是否一定需要呢?在什么情况下一定需要呢?
2、我上面说的有不对的地方么?请大家帮我纠正!因为,我刚开始学,所以,想纠正一些错误的理解。
谢谢大家了! UP有分!