開發工具：Microsoft Visual Studio 2005
數據庫:Microsoft SQL Server 2005
說明：這裏建立的數據庫名爲Demo,有一個學生表Student,爲操作方便起見,我只添加兩個字段:studentnum和studentname.
一、SQL語句:
--create database Demo
use Demo
create table Student
(
studentnum char(14) primary key,
studentname varchar(30) not null
)
insert into Student values('20041000010201','張揚')
二、代碼：
1.引入名稱空間:using System.Data.SqlClient;
2.定義連接字符串,連接對象，命令對象:
private String connectionstr;
private SqlConnection connection;
private SqlCommand command;
3.在構造函數中初始化連接字符串，連接對象，命令對象
(1)初始化連接字符串：
方式① connectionstr="server=localhost;uid=sa;pwd=123456;database=Demo";
方式② connectionstr="server=127.0.0.1";Integrade Security=SSPI;database=Demo";
其中，SIMS是我要連接的數據庫名.(1)中的uid 和pwd是你登錄數據庫的登錄名和密碼
注：這種連接是連接本地的數據庫，若要連接局域網內其它機子上的數據庫，可將方式①的"server=localhost;"改爲"server=數據庫所在機子的IP;"
(2)初始化連接對象
connection = new SqlConnection(connectionstr);
(3)初始化命令對象
command =new SqlCommand();
command .Connection =connection ;
4.操作數據庫中的數據
(1)查詢數據庫中的數據
方法一：
string snum=tBstudentnum .Text .Trim ();
string str = "select * from Student where studentnum='" + snum + "'";
command .CommandText =str;
connection.Open();
if (command.ExecuteScalar() == null)
{
MessageBox.Show("您輸入的學號對應的學生不存在！", "錯誤", MessageBoxButtons.OK,MessageBoxIcon.Error);
}
else
{
SqlDataReader sdr = command.ExecuteReader();
while (sdr.Read())
{
tBstudentnum .Text = sdr["studentnum"].ToString();
tBstudentname.Text = sdr["studentname"].ToString();
}
sdr.Close();
}
connection.Close();
方法二：
string snum=tBstudentnum .Text .Trim ();
string str = "select * from Student where studentnum='" + snum + "'";
command .CommandText =str;
connection.Open();
if (command.ExecuteScalar() == null)
{
MessageBox.Show("您輸入的學號對應的學生不存在！", "錯誤", MessageBoxButtons.OK,MessageBoxIcon.Error);
}
else
{
SqlDataAdapter sda = new SqlDataAdapter(str,connection );
DataSet ds = new DataSet();
sda.Fill(ds, "Student");
DataTable dt = ds.Tables["Student"];
tBstudentnum.Text = dt.Rows[0]["studentnum"].ToString();
tBstudentname.Text = dt.Rows[0]["studentname"].ToString();
}
connection.Close();
(2)向數據庫中添加數據
方法一:
string snum = tBstudentnum.Text.Trim ();
string sname = tBstudentname.Text.Trim();
if (snum == "" || sname == "")
{
MessageBox.Show("學生學號或姓名不能爲空！", "錯誤", MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
else
{
string insertstr="insert into Student values('"+snum +"','"+sname +"')";
command.CommandText = insertstr;
connection.Open();
command.ExecuteNonQuery();
MessageBox.Show("學生添加成功！", "提示", MessageBoxButtons.OK,
MessageBoxIcon.Information);
connection.Close();
}
方法二:
string str = "select * from Student";
string insertstr = "insert into Student values('" + snum + "','" + sname + "')";
SqlDataAdapter sda = new SqlDataAdapter(str, connection);
DataSet ds = new DataSet();
sda.Fill(ds, "Student");
DataTable dt = ds.Tables["Student"];
DataRow dr = dt.NewRow();
dr["studentnum"] = snum;
dr["studentname"] = sname;
dt.Rows.Add(dr);
sda.InsertCommand = new SqlCommand(insertstr, connection);
sda.Update(ds, "Student");
MessageBox.Show("學生添加成功！", "提示", MessageBoxButtons.OK,
MessageBoxIcon.Information);
(3)修改數據庫中的數據
方法一:
string snum = tBstudentnum.Text.Trim();
string sname = tBstudentname.Text.Trim();
if (snum == "" || sname == "")
{
MessageBox.Show("學生學號或姓名不能爲空！", "錯誤", MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
else
{
string modifystr = "update Student set studentname='" + sname +
"' where studentnum='" + snum + "'";
command.CommandText = modifystr;
connection.Open();
command.ExecuteNonQuery();
MessageBox.Show("學生的姓名修改成功！", "提示", MessageBoxButtons.OK,
MessageBoxIcon.Information );
connection.Close();
方法二:
string snum = tBstudentnum.Text.Trim();
string sname = tBstudentname.Text.Trim();
if (snum == "" || sname == "")
{
MessageBox.Show("學生學號或姓名不能爲空！", "錯誤", MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
else
{
string str = "select * from Student where studentnum='" + snum + "'"; ;
string updatestr = "update Student set studentname='" + sname +
"' where studentnum='" + snum + "'";
SqlDataAdapter sda = new SqlDataAdapter(str, connection);
DataSet ds = new DataSet();
sda.Fill(ds, "Student");
DataTable dt = ds.Tables["Student"];
dt.Rows[0]["studentname"] = sname;
sda.UpdateCommand = new SqlCommand(updatestr , connection);
sda.Update(ds, "Student");
MessageBox.Show("學生姓名修改成功！", "提示", MessageBoxButtons.OK,
MessageBoxIcon.Information);
}
(4)刪除數據庫中的數據
方法一:
string snum = tBstudentnum.Text.Trim();
if (snum == "")
{
MessageBox.Show("學生學號不能爲空！", "錯誤", MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
else
{
string str = "select * from Student where studentnum='" + snum + "'";
string deletestr = "delete from Student where studentnum='" + snum + "'";
command.CommandText =str ;
connection.Open();
if (command.ExecuteScalar() == null)
{
MessageBox.Show("此學號對應的學生不存在！", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
else
{
command.CommandText = deletestr;
command.ExecuteNonQuery();
MessageBox.Show("學生的信息刪除成功！", "提示", MessageBoxButtons.OK,
MessageBoxIcon.Information);
}
connection.Close();
方二:
string str = "select * from Student where studentnum='" + snum + "'";
string deletestr = "delete from Student where studentnum='" + snum + "'";
SqlDataAdapter sda = new SqlDataAdapter(str, connection);
DataSet ds = new DataSet();
sda.Fill(ds, "Student");
DataTable dt = ds.Tables["Student"];
if (dt.Rows.Count > 0)
{
dt.Rows[0].Delete();
sda.DeleteCommand = new SqlCommand(deletestr, connection);
sda.Update(ds, "Student");
MessageBox.Show("學生信息刪除成功！", "提示", MessageBoxButtons.OK,
MessageBoxIcon.Information);
}
else
{
MessageBox.Show("此學號對應的學生不存在！", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
PS:以上對數據庫的操作,大都從操作角度出發僅進行單一的操作,有的地方並未進行錯誤處理,如修改學生信息時,學號應不可能編輯等.
