添加，删除，更新数据庫

1）如果不返回行，用以下语句：



private void button1_Click(object sender, EventArgs e)




...{


SqlConnection con = new SqlConnection();


con.ConnectionString = (@"Data source=localhost;Integrated Security=true;database=Northwind");


try




...{


string SQL = "UPDATE Categories SET CategoryName='" + textBox1.Text + "'" + " WHERE CategoryID='1'";


SqlCommand cmd = new SqlCommand();


cmd.CommandText = SQL;


cmd.Connection = con;


con.Open();




int rowAffected = cmd.ExecuteNonQuery();


if (rowAffected == 1)


label1.Text = "Updated sucessuflly!";








}


catch (SqlException es)




...{


MessageBox.Show(es.Message);


}

2）如果要返回单值(行)的查询，用以下语句：

//cmd.ExecuteNonQuery();
int intCustomerIDOrdinal = Convert.ToInt32(cmd.ExecuteScalar());//返回一个表示列序号的整数
string strCategoryName = Convert.ToString(cmd.ExecuteScalar());//单值查询

　3）调用存储过程
private void button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = (@"Data source=localhost;Integrated Security=true;database=Northwind");
try
{
// string SQL = "UPDATE Categories SET CategoryName='" + textBox1.Text + "'" + " WHERE CategoryID='1'";
SqlCommand cmd = con.CreateCommand();
con.Open();
cmd.CommandText = "GetCustomer";
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("@CustomerID", SqlDbType.NChar, 5).ToString();
cmd.Parameters[0].Value = "ALFKI";

SqlDataReader reader = cmd.ExecuteReader();

}
catch (SqlException es)
{
MessageBox.Show(es.Message);
}
存储过程如下：
CREATE PROCEDURE GetCustomer(@CustomerID nChar(5))
AS
SELECT CustomerID,CompanyName,ContactName,ContactTitle
FROM Customers WHERE CustomerID=@CustomerID

4)调用ExecuteNonQuery方法执行储存在Command中的查询:
示例将订单细节提取到一个DataTable中，修改订单内容，再向数据提交更改。
private void button1_Click(object sender, EventArgs e)
{

SqlConnection con = new SqlConnection();
string sql = "SELECT * FROM Employees";
con.ConnectionString = @"Data source=localhost;Integrated Security=true;database=Northwind";
try
{
con.Open();
DataTable tb1;
tb1=GetTable();//初始化表
ResetOrder();//更新表(插入，删除)
SqlDataAdapter ad = new SqlDataAdapter(sql,con);
ad.Fill(tb1);

}
catch (SqlException es)
{
MessageBox.Show(es.Message);
}
}

static DataTable GetTable()
{
DataTable tb1 = new DataTable("Employees");
DataColumn col;
col = tb1.Columns.Add("EmployeeID", typeof(int));
col.AllowDBNull = false;
col = tb1.Columns.Add("LastName",typeof(string));
col.AllowDBNull = false;
tb1.PrimaryKey = new DataColumn[] { tb1.Columns["OrderID"], tb1.Columns["ProductID"] };
return tb1;
}
static void ResetOrder()
{
string strSQL;

SqlConnection con = new SqlConnection();
con.ConnectionString = (@"Data source=localhost;Integrated Security=true;database=Northwind");
con.Open();
SqlCommand cmd = con.CreateCommand();
//插入一行
strSQL = "INSERT INTO Employees(FirstName,LastName,Notes) VALUES('firstname','lastname','notes')";
cmd.CommandText=strSQL;
cmd.ExecuteNonQuery();
//删除一行
strSQL="DELETE FROM Employees WHERE EmployeeID='112237'";
cmd.CommandText = strSQL;
cmd.ExecuteNonQuery();

}
}