请问这个问题如何解决?

弄好了,不过有以下缺点:
B表要自己手动建立,而且数据量超大的话可能速度不理想.
以下是代码:
DataTable dt = new DataTable();
SqlConnection conn = new SqlConnection(@"Data Source=yh\sqlexpress;Initial Catalog=test;Integrated Security=True");
SqlConnection conn2 = new SqlConnection(@"Data Source=yh\sqlexpress;Initial Catalog=test2;Integrated Security=True");
string sql_sel = "select * from a";
SqlCommand cmd2 = new SqlCommand(sql_sel, conn2);

SqlDataAdapter da = new SqlDataAdapter(cmd2);
conn2.Open();
da.Fill(dt);
conn2.Close();

conn.Open();

string sql = "";
for (int i = 0; i < dt.Rows.Count; i++)
{//对datatable循环
sql = "insert into b(id) values ('" + dt.Rows[i]["id"].ToString() + "'