C# 跟查询有关的代码
时间：2011-03-20 来源：beeone
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace hetaoTest
{
public partial class Form1 : Form
{
static SqlConnection conn = null;
public Form1()
{
InitializeComponent();
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
}
/// <summary>
/// 添加的方法
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button1_Click(object sender, EventArgs e)
{
try
{
{
string conStr = "Data Source=127.0.0.1;Initial Catalog=TestDB;Integrated Security=True";
conn = new SqlConnection(conStr);
conn.Open();
SqlCommand cmd = conn.CreateCommand();
//-----------------------------添加方法1-----------------------------
//cmd.CommandText = "insert into T_UserName(name,age)Values('" + txtName.Text.Trim() + "','"
// + txtAge.Text.Trim() + "')";
//-----------------------------添加方法2-----------------------------
cmd.CommandText = "INSERT INTO T_UserName(name,age)VALUES(@name,@age)";
//cmd.Parameters.AddWithValue("@name",txtName.Text.Trim());
//cmd.Parameters.AddWithValue("@age",txtAge.Text.Trim());
//-----------------------------添加方法3-----------------------------
cmd.Parameters.Add("@name", SqlDbType.VarChar);
cmd.Parameters["@name"].Value = txtName.Text.Trim();
cmd.Parameters.Add("@age", SqlDbType.VarChar);
cmd.Parameters["@age"].Value = txtAge.Text.Trim();
if (MessageBox.Show("确定添加么？", "My Application", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
== DialogResult.Yes)
{
cmd.ExecuteNonQuery();
}
}
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}
/// <summary>
/// 使用sqlcommand对象来返回数据集合的方法
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void Form1_Load(object sender, EventArgs e)
{
string connStr = "Data Source=127.0.0.1;Initial Catalog=TestDB;Integrated Security=True";
string SqlStr = "SELECT * FROM T_UserName";
SqlConnection conn = new SqlConnection(connStr);
conn.Open();
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = SqlStr;
//int flat = (int)(cmd.ExecuteScalar());
//MessageBox.Show(Convert.ToString(flat));
SqlDataAdapter adp = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
adp.Fill(dt);
dataGridView1.DataSource = dt;
}
/// <summary>
///
///使用sqlcommand对象来返回SQL执行正确与否
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnScan1_Click(object sender, EventArgs e)
{
string connStr = "Data Source=127.0.0.1;Initial Catalog=TestDB;Integrated Security=True";
string sqlStr = "SELECT * FROM T_UserName1";
SqlConnection conn = new SqlConnection(connStr);
conn.Open();
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = sqlStr;
try
{
cmd.ExecuteNonQuery();
MessageBox.Show("成功查询", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Question);
}
catch
{
MessageBox.Show("查询失败", "提示", MessageBoxButtons.OK, MessageBoxIcon.Question);
}
}
private void button2_Click(object sender, EventArgs e)
{
Application.Exit();
}
/// <summary>
/// 使用sqlcommand对象来操作存储过程
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button4_Click(object sender, EventArgs e)
{
string strconn = "Data Source=127.0.0.1;Initial Catalog=TestDB;Integrated Security=True";
SqlConnection conn = new SqlConnection(strconn);
conn.Open();
SqlCommand sqlcmd = new SqlCommand();
sqlcmd.CommandText = "a";
sqlcmd.CommandType = CommandType.StoredProcedure;
sqlcmd.Connection = conn;
//sqlcmd.Parameters.Add("@param1", textBox1.Text.Trim());
//sqlcmd.Parameters.Add("@param2", textBox2.Text.Trim());
//sqlcmd.Parameters.Add("@param3", textBox3.Text.Trim());
SqlDataAdapter adp = new SqlDataAdapter(sqlcmd);
DataTable dt = new DataTable();
adp.Fill(dt);
dataGridView1.DataSource = dt;
}
private void button3_Click(object sender, EventArgs e)
{
string connStr = "Data Source=127.0.0.1;Initial Catalog=TestDB;Integrated Security=True";
string SqlStr = "SELECT * FROM T_UserName";
SqlConnection conn = new SqlConnection(connStr);
conn.Open();
SqlCommand cmd =new SqlCommand(SqlStr,conn);
SqlDataReader dr = cmd.ExecuteReader();//返回只能读取,不能写入的SqlDataReader对象
while (dr.Read())
{
MessageBox.Show("ID："+dr.GetValue(0)+" Name: "+dr.GetValue(1)+" Age: "+dr.GetValue(2)+" Sex: "+dr.GetValue(3));
}
}
/// <summary>
/// ExecuteNonQuery方法
///一般修改,删除,插入都用它
///返回受影响的行数。
/// sql="update 表 set 栏位1=值1，栏位2=值2 where (条件);"
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button5_Click(object sender, EventArgs e)
{
string connStr = "Data Source=127.0.0.1;Initial Catalog=TestDB;Integrated Security=True";
string sqlStr = "Update T_UserName set name='Admin',Age='100',Sex='男' where(ID=66)";
SqlConnection conn = new SqlConnection(connStr);
conn.Open();
SqlCommand cmd = new SqlCommand(sqlStr,conn);
cmd.ExecuteNonQuery();
MessageBox.Show("修改成功！");
}
}
}
ExecuteScalar方法
执行查询，并返回查询所返回的结果集中第一行的第一列。所有其他的列和行将被忽略。
using System;
using System.Data.SqlClient;
public class Lvcha
{
public static void Main(string[] args)
{
string source="Server =192.168.1.100; User ID=ac_sy_guest; Password=guest1314; Initial CataLog=Account";
string select="select count(*) from dbUser";
SqlConnection conn=new SqlConnection(source);
conn.Open();
SqlCommand cmd=new SqlCommand(select,conn);
object o=cmd.ExecuteScalar();
Console.WriteLine(o);
Console.ReadLine();
}
}
ExecuteNonQuery用于执行不返回任何记录的SQL语句或存储过程。在数据库执行如更新、插入、删除操作时，应使用这个方法。ExecuteNonQuery返回一个整数值，用来说明受查询语句影响的行数。
connection.Open();
command.ExecuteNonQuery();
command.Close();
ExecuteScalar与ExecuteNonQuery一样，其返回的也是单值，但该返回值是从数据库中读出来的，而不是受影响的行数。它通常用于选择一个值的SQL语句。如果SELECT返回多行或多列，则使用该方法仅返回第一行第一列的数据。
ExecuteReader被用于返回多条记录的SELECT语句（包含任意个字段）。ExecuteReader将返回一个包含查询结果的SqlDataReader对象。一个SqlDataReader对象是以顺序向前且只读的形式逐个读取并返回结果的。SqlDataReader是数据库中读取数据最快的对象，但必须打开连接。通过SqlDataReader取回所有的记录，并把它们存入DataTable对象中（它可以存储离线数据而不需要一个打开的连接），这样就可以马上关闭数据库连接了。DataTable类可以存放本地的结果集而不需要一个打开的SQL Server连接，和其它的ADO.NET对象一样，它也不是特定于某种数据提供程序的。
conn.Open();
SqlDataReader reader = comm.ExecuteReader();
DataTable table = new DataTable();
table.Load(reader);
reader.Close();
conn.Close();
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