C#操作数据库总结 C#操作数据库总结(vs2005+sql2005)

时间:2021-03-19 人气:0

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开发工具：Microsoft Visual Studio 2005
数据库:Microsoft SQL Server 2005
说明：这里建立的数据库名为Demo,有一个学生表Student,为操作方便起见,我只添加两个字段:studentnum和studentname.
一、SQL语句:

复制代码代码如下:

 
--create database Demo 
use Demo 

create table Student 
( 
studentnum char(14) primary key, 
studentname varchar(30) not null 
) 
insert into Student values('20041000010201','张扬') 

二、代码：
1.引入名称空间:using System.Data.SqlClient;
2.定义连接字符串,连接对象，命令对象:
private String connectionstr;
private SqlConnection connection;
private SqlCommand command;
3.在构造函数中初始化连接字符串，连接对象，命令对象

(1)初始化连接字符串：
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是我要连接的数据库名.(1)中的uid 和pwd是你登录数据库的登录名和密码
注：这种连接是连接本地的数据库，若要连接局域网内其它机子上的数据库，可将方式①的"server=localhost;"改为"server=数据库所在机子的IP;"

复制代码代码如下:

 
// 连接字符串：String connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=product.mdb"; 
// 建立连接：OleDbConnection connection = new OleDbConnection(connectionString); 
// 使用OleDbCommand类来执行Sql语句： 
// OleDbCommand cmd = new OleDbCommand(sql, connection); 
// connection.Open(); 
// cmd.ExecuteNonQuery(); 
#endregion 

#region 连接字符串 
//string strcon = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\程序书籍软件\c#程序代码\access数据库操作\addressList.mdb"; //绝对路径 
// string strcon = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+Environment.CurrentDirectory+"\\addressList.mdb"; //相对路径 

(2)初始化连接对象
connection = new SqlConnection(connectionstr);
(3)初始化命令对象
command =new SqlCommand();
command .Connection =connection ;
4.操作数据库中的数据
(1)查询数据库中的数据
方法一：

复制代码代码如下:

 
string snum=tBstudentnum .Text .Trim (); 
string str = "select * from Student where studentnum='" + snum + "'"; 
command .CommandText =str; 
connection.Open(); 
if (command.ExecuteScalar() == null) 
{ 
MessageBox.Show("您输入的学号对应的学生不存在！", "错误", 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：

复制代码代码如下:

 
string snum=tBstudentnum .Text .Trim (); 
string str = "select * from Student where studentnum='" + snum + "'"; 
command .CommandText =str; 
connection.Open(); 
if (command.ExecuteScalar() == null) 
{ 
MessageBox.Show("您输入的学号对应的学生不存在！", "错误", 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)向数据库中添加数据
方法一:

复制代码代码如下:

 
string snum = tBstudentnum.Text.Trim (); 
string sname = tBstudentname.Text.Trim(); 
if (snum == "" || sname == "") 
{ 
MessageBox.Show("学生学号或姓名不能为空！", "错误", MessageBoxButtons.OK, 
MessageBoxIcon.Error); 
} 
else 
{ 
string insertstr="insert into Student values('"+snum +"','"+sname +"')"; 
command.CommandText = insertstr; 
connection.Open(); 
command.ExecuteNonQuery(); 
MessageBox.Show("学生添加成功！", "提示", MessageBoxButtons.OK, 
MessageBoxIcon.Information); 
connection.Close(); 
} 

方法二:

复制代码代码如下:

 
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("学生添加成功！", "提示", MessageBoxButtons.OK, 
MessageBoxIcon.Information); 

(3)修改数据库中的数据
方法一:

复制代码代码如下:

 
string snum = tBstudentnum.Text.Trim(); 
string sname = tBstudentname.Text.Trim(); 
if (snum == "" || sname == "") 
{ 
MessageBox.Show("学生学号或姓名不能为空！", "错误", MessageBoxButtons.OK, 
MessageBoxIcon.Error); 
} 
else 
{ 
string modifystr = "update Student set studentname='" + sname + 
"' where studentnum='" + snum + "'"; 
command.CommandText = modifystr; 
connection.Open(); 
command.ExecuteNonQuery(); 
MessageBox.Show("学生的姓名修改成功！", "提示", MessageBoxButtons.OK, 
MessageBoxIcon.Information ); 
connection.Close(); 

方法二:

复制代码代码如下:

 
string snum = tBstudentnum.Text.Trim(); 
string sname = tBstudentname.Text.Trim(); 
if (snum == "" || sname == "") 
{ 
MessageBox.Show("学生学号或姓名不能为空！", "错误", 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("学生姓名修改成功！", "提示", MessageBoxButtons.OK, 
MessageBoxIcon.Information); 
} 

(4)删除数据库中的数据
方法一:

复制代码代码如下:

 
string snum = tBstudentnum.Text.Trim(); 
if (snum == "") 
{ 
MessageBox.Show("学生学号不能为空！", "错误", 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("此学号对应的学生不存在！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); 
} 
else 
{ 
command.CommandText = deletestr; 
command.ExecuteNonQuery(); 
MessageBox.Show("学生的信息删除成功！", "提示", MessageBoxButtons.OK, 
MessageBoxIcon.Information); 
} 
connection.Close(); 

方二:

复制代码代码如下:

 
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("学生信息删除成功！", "提示", MessageBoxButtons.OK, 
MessageBoxIcon.Information); 
} 
else 
{ 
MessageBox.Show("此学号对应的学生不存在！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error); 
} 

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