用VB创建了SQL数据库，如何写代码，选择数据库、用户名和密码进入

Answer 1

要连接SQL数据库有两种方法用ADODC或ADO.
方法一: （ADODC)
首先须引用Projects-Components-Microsoft ADO Data Controls 6.0 (OLEDB).
之后在表单设置ADODC控件。然后Form_Load()输入以下代码：

Private Sub Form_Load()
ADODC1.ConnectionString = "Provider=SQLOLEDB;Password=密码;Persist Security Info=False;User ID=用户名;Initial Catalog=数据库名;Data Source=服务器名"

ADODC1.CommandType = adCmdText
ADODC1.RecordSource = "select * from 表格名称"
ADODC1.Refresh
End Sub

方法二: (ADO)

'首先须引用Projects-References-Microsoft Active X Data Objects 2.0 Library.

'*注意以下两段须写在程式最上面（Gerenal一般）中。

Dim cn As New ADODB.Connection
Dim rs As New ADODB.Recordset
Dim SQL As String

'然后在Form_Load()输入以下代码：
Private Sub Form_Load()
cn.ConnectionString = "Provider=SQLOLEDB;Password=密码;Persist Security Info=False;User ID=用户名;Initial Catalog=数据库名;Data Source=服务器名"
cn.Open

If rs.State = adStateOpen Then rs.Close
rs.CursorLocation = adUseClient
SQL = "select * from 表格名"
rs.Open Trim$(SQL), cn, adOpenKeyset, adLockPessimistic
End Sub

Answer 2

Set conn = New ADODB.Connection '定义数据库的连接
conn.ConnectionString = "Provider=sqloledb;Data Source=(local);Initial Catalog=books_mag;User Id=sa;Password=sa;"
conn.ConnectionTimeout = 5
conn.Open

Answer 3

string str = "Data Source=.;Initial Catalog=数据库名;User ID=sa;Password=sa";
SqlConnection conn = new SqlConnection(str);
conn.Open();