stringsql

‘壹’ c#连接mysql的字符串 应该怎么写

这里将介绍C#数据库查询和操作方面的有关知识，包括数据库连接、数据库查询的相关代码和示例。希望本文对大家有所帮助。

一：C#数据库查询之数据库连接代码：

SqlConnectionobjSqlConnection=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); objSqlConnection.Open(); 二：数据库的添加记录代码：

inti=0; strings1="",s2=""; i=Convert.ToInt16(textBox1.Text); s1=textBox2.Text; s2=textBox3.Text; SqlConnectionobjSqlConnection=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); objSqlConnection.Open(); MessageBox.Show("数据库连接成功","好"); try { SqlCommandsqlcom=newSqlCommand("insertintoinfo(id,name,sex)values("+i+",'"+s1+"','"+s2+"')",objSqlConnection); sqlcom.ExecuteNonQuery(); MessageBox.Show("添加成功！","啊"); } catch(Exceptiona) { MessageBox.Show(a.ToString()); } MessageBox.Show("添加成功！","啊"); } 三：数据库的修改代码：

inti=0; strings1="",s2=""; s1=textBox2.Text; s2=textBox3.Text; if(textBox1.Text.Length==0) i=0; else i=Convert.ToInt32(textBox1.Text); SqlConnectionobjSqlConnection=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); objSqlConnection.Open(); MessageBox.Show("数据库连接成功","好"); try { SqlCommandsqlcom=newSqlCommand("updateinfosetname='"+s1+"',sex='"+s2+"'"+"whereid="+i,objSqlConnection); sqlcom.ExecuteNonQuery(); MessageBox.Show("修改成功！","啊"); objSqlConnection.Close(); } catch(Exceptiona) { MessageBox.Show(a.ToString()); } 四：数据库的删除代码：

inti=0; strings1="",s2=""; s1=textBox2.Text; s2=textBox3.Text; if(textBox1.Text.Length==0) i=0; else i=Convert.ToInt16(textBox1.Text); SqlConnectionobjSqlConnection=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); objSqlConnection.Open(); MessageBox.Show("数据库连接成功","好"); try { SqlCommandsqlcom=newSqlCommand("deletefrominfowhereid="+i,objSqlConnection); sqlcom.ExecuteNonQuery(); MessageBox.Show("删除成功！","啊"); objSqlConnection.Close(); } catch(Exceptiona) { MessageBox.Show(a.ToString()); } 五：数据库的查询代码：

1.类开始：

DataTabledt1=newDataTable(); SqlDataAdapterda1=newSqlDataAdapter(); 2.按钮代码：

inti=0,n=0; strings1="",s2=""; s1=textBox2.Text; s2=textBox3.Text; if(textBox1.Text.Length==0) i=0; else i=Convert.ToInt32(textBox1.Text); SqlConnectionobjSqlConnection=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); objSqlConnection.Open(); MessageBox.Show("数据库连接成功","好"); stringquery="SELECT*frominfowhereid="+i; DataSetobjDataSet=newDataSet(); SqlDataAdapterobj=newSqlDataAdapter(); obj.SelectCommand=newSqlCommand(query,objSqlConnection); obj.Fill(objDataSet,"info"); SqlCommandobjSqlCommand=newSqlCommand(query,objSqlConnection); SqlDataReaderobjSqlReader=objSqlCommand.ExecuteReader(); while(objSqlReader.Read()) { n+=1; MessageBox.Show("编号:"+objSqlReader.Getvalue(0)+"姓名:"+objSqlReader.Getvalue(1)+"性别"+objSqlReader.Getvalue(2)); } if(n==0) MessageBox.Show("数据库中没有这样的记录！"); 六：C#数据库查询代码：

inti=0; //intn=0; strings1="",s2=""; stringsql; s1=textBox2.Text; s2=textBox3.Text; if(textBox1.Text.Length==0) { i=0; } else i=Convert.ToInt32(textBox1.Text); SqlConnectionobjSqlConnection=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); objSqlConnection.Open(); MessageBox.Show("数据库连接成功","好"); stringquery="SELECT*frominfowhereid="+i; if(i==0) sql="select*frominfo"; else sql="select*frominfowhereid="+i; da1=newSqlDataAdapter(sql,objSqlConnection); dt1.Clear(); da1.Fill(dt1); dataGridView1.DataSource=dt1; C#数据库查询之数据库的封装类代码：

classDBClass { publicvoiddbclass(stringsql) { try { SqlConnectionsqlcon=newSqlConnection("server=127.0.0.1;uid=sa;pwd=;database=test"); sqlcon.Open(); SqlTransactionobjt=sqlcon.BeginTransaction();//事物开始 SqlCommandsqlcom=newSqlCommand(sql,sqlcon); sqlcom.Transaction=objt;//将Command对象设置为事物处理的对象 sqlcom.ExecuteNonQuery(); objt.Commit();//提交事物 sqlcon.Close(); } catch(Exceptiona) { MessageBox.Show(a.ToString()); } } } --db2数据库连接代码： stringstrcon="Provider=IBMDADB2;DataSource=hfzd;UserId=db2admin;Password=db2admin"; //stringsql="select*fromADMINISTRATOR.HFZD"; stringsql="deletefromADMINISTRATOR.HFZDwhereID=1"; OleDbConnectionolecon=newOleDbConnection(strcon); olecon.Open(); MessageBox.Show("数据库已连接上"); dt.Clear(); da=newOleDbDataAdapter(sql,olecon); da.Fill(dt); dataGridView1.DataSource=dt; olecon.Close();

‘贰’ java 将数据保存到数据库的问题 SQL语句

先将T表中得到的结果集存在数组中,最后是以javabean那样的.然后得到name
id
sex
相对应然后插入进去!如果只是一条数据,那就更简单了,直接用变量得到后,编写插入的SQL语句,然后执行就行了

‘叁’ JAVA 关于调用数据库

<%
DbConnect
db
=
DbConnect.getInstance();//获取一个连接实例
Connection
conn
=
db.getConnect();//取得一个连接
String
sql="select
*from
(select
*from
notice_hanchao
order
by
insert_time
desc)";//一个查询字符串
PreparedStatement
ps
=
conn.prepareStatement(sql);//把查询字符串构造成一个语句对象
ResultSet
rs
=
ps.executeQuery();//执行语句，并返回一个结果集
%>

‘肆’ java怎样连接mysql数据库

1、java连接MySQL数据库需要有一个驱动jar包

例如：mysql-connector-java-5.1.26-bin.jar,

package.test.jsp;
importjava.sql.Connection;
importjava.sql.DriverManager;
importjava.sql.ResultSet;
importjava.sql.SQLException;
importjava.sql.Statement;

importjavax.naming.spi.DirStateFactory.Result;

publicclassDbConnection{
privatestaticConnectionconn;
publicDbConnection(){
Stringdrivername="com.mysql.jdbc.Driver";
Stringusername="root";
Stringurl="jdbc:mysql://localhost/jsptest?useUnicode=true&characterEncoding=UTF-8";
Stringpassword="";
//加载驱动
try{
Class.forName(drivername);
}catch(ClassNotFoundExceptione){
System.out.println("驱动加载失败！");
e.printStackTrace();
}
//建立连接
try{
conn=DriverManager.getConnection(url,username,password);
}catch(SQLExceptione){
System.out.println("数据库连接失败！");
e.printStackTrace();
}


}
//getResultSet
publicResultSetGetResultSet(Stringsql)
{
ResultSetrs=null;
//statemanage
try{
Statementst=conn.createStatement();
rs=st.executeQuery(sql);
}catch(SQLExceptione){
System.out.println("状态管理器创建失败");
e.printStackTrace();
}
returnrs;

}
//DML
publicintDML(Stringsql)
{
intcount=-1;
try{
Statementstatement=conn.createStatement();
count=statement.executeUpdate(sql);
}catch(SQLExceptione){
System.out.println("状态管理器创建失败");
e.printStackTrace();
}
returncount;
}
}

3、可以新建service类来调用连接类里面的getResultSet方法和DML，实现自己所需用的功能。

‘伍’ 写一段代码

数据库的建立应该不用再讲了吧，现在讲使用JAVA与数据库进行交互使用JDBC进行数据库的增删改查操作1.下载MicrosoftSQLServer2005JDBC驱动包jar文件将jar文件引入工程中2.封装数据库链接的获取和关闭操作importjava.sql.*;publicclassBaseDao{/***数据库驱动类的字符串,完整的包名加类名在工程中查看添加的jar文件能看到这个类*/privatestaticfinalStringDRIVE="com.microsoft.sqlserver.jdbc.SQLServerDriver";/***数据库连接地址**DataBaseName=数据库名称其它固定*/privatestaticfinalStringURL="jdbc:sqlserver://localhost:1433;DataBaseName=bbs";/***连接数据库的用户名*/privatestaticfinalStringUSER="sa";/***用户密码*/="";/***获取连接异常直接抛出或者捕获后自定义异常信息再抛出*/()throwsException{Class.forName(DRIVE);returnDriverManager.getConnection(URL,USER,PASSWORD);}/***关闭与数据库的连接释放资源*/publicstaticvoidcloseAll(ResultSetresultSet,PreparedStatementpst,Connectionconnection)throwsException{if(resultSet!=null)resultSet.close();if(pst!=null)pst.close();if(connection!=null)connection.close();}}3.创建图书的实体类publicclassBook{/***数据库主键*/privateLongid;/***作者*/privateStringauthor;/***书名*/privateStringname;/***默认构造**/publicBook(){}/***全字段构造*@paramid*@paramauthor*@paramname*/publicBook(Longid,Stringauthor,Stringname){this.id=id;this.author=author;this.name=name;}/***以下为读写属性的方法*@return*/publicStringgetAuthor(){returnauthor;}publicvoidsetAuthor(Stringauthor){this.author=author;}publicLonggetId(){returnid;}publicvoidsetId(Longid){this.id=id;}publicStringgetName(){returnname;}publicvoidsetName(Stringname){this.name=name;}}4.创建与图书表交互的工具类importjava.sql.Connection;importjava.sql.PreparedStatement;importjava.sql.ResultSet;importjava.util.ArrayList;importjava.util.List;publicclassBookDao{/***添加新书**@parambook要添加入数据库的图书作者书名必须给定*/publicvoidaddBook(Bookbook)throwsException{//连接Connectionconnection=null;//执行语句PreparedStatementpst=null;try{connection=BaseDao.getConnection();//构造执行语句Stringsql="insertintobookvalues("+book.getAuthor()+","+book.getName()+")";pst=connection.prepareStatement(sql);pst.executeUpdate();}catch(Exceptione){//抛出异常throwe;}finally{//无论是否异常均关闭数据库BaseDao.closeAll(null,pst,connection);}}/***查询所有书籍列表*/publicListgetBooks()throwsException{//用于存放查寻结果的集合Listbooks=newArrayList();//连接Connectionconnection=null;//执行语句PreparedStatementpst=null;//查询结果ResultSetresultSet=null;try{connection=BaseDao.getConnection();//构造查询语句Stringsql="select*frombook";pst=connection.prepareStatement(sql);resultSet=pst.executeQuery();//循环读取查询结果行while(resultSet.next()){//getXXX的参数为数据表列名Bookbook=newBook(resultSet.getLong("id"),resultSet.getString("author"),resultSet.getString("name"));//将封装好的图书对象存入集合books.add(book);}}catch(Exceptione){//抛出异常throwe;}finally{//无论是否异常均关闭数据库BaseDao.closeAll(resultSet,pst,connection);}//返回查询结果returnbooks;}/***其它方法类似上面只是语句不同*/}当然以上只是简单的封装初学者可以在理解以上代码的基础上进行更高级的封装5.使用BookDao添加书籍和获取所有书籍列表importjava.util.List;/***测试类*@authorAdministrator**/publicclassTest{/***@paramargs*@throwsException*/publicstaticvoidmain(String[]args)throwsException{//创建工具类对象BookDao=newBookDao();//创建一本图书Bookbook=newBook(null," :495691293","编程菜鸟");//添加书籍到数据库.addBook(book);//获取所有图书列表Listbooks=.getBooks();//输出结果for(Bookb:books){System.out.println(b.getId()+"\t"+b.getAuthor()+"\t"+b.getName());}}}

‘陆’ 关于jsp连SQL的疑问

public
ResultSet
select(String
sql)
//查询数据函数
{
try
{
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_
INSENSITIVE
,ResultSet.CONCUR_READ_ONLY);
rs=stmt.executeQuery(sql);
}
catch(
Exception
e)
{
e.printStackTrace();
}
你是直接调用
这个方法的，可是这个方法中的conn是null的啊！没有值啊！
如果不想动的话，把public
void
getConnect()
这个方法里的内容写到静态代码块内。或无参构造内。

‘柒’ visual studio怎么做数据库

publicclassStudentService
{

//从配置文件中读取数据库连接字符串
=ConfigurationManager.ConnectionStrings["accpConnectionString"].ToString();
=ConfigurationManager.ConnectionStrings["DataBaseOwner"].ToString();
AdoNetModels.Studentmodel=newStudent();
//conststringspName=".usp_DeleteStudent";

#region删除数据1
publicintDeleteStudent(intstuID)
{
intresult=0;
//数据库连接Connection对象
SqlConnectionconnection=newSqlConnection(connString);
//构建删除的sql语句
stringsql=string.Format("DeleteFromStudentWherestuID={0}",stuID);
//定义command对象
SqlCommandcommand=newSqlCommand(sql,connection);

try
{
connection.Open();
result=command.ExecuteNonQuery();//执行命令
}
catch(Exceptionex)
{

Console.WriteLine(ex.Message);
}
finally
{
connection.Close();
}
returnresult;
}
#endregion

#region删除数据2

publicintDeleteStudent2(intstuID)
{
intresult=0;
//构建删除的sql语句使用参数
stringsql="DeleteFromStudentWherestuID=@stuID";

using(SqlConnectionconnection=newSqlConnection(connString))
{
SqlCommandobjCommand=newSqlCommand(sql,connection);

objCommand.Parameters.Add("@stuID",SqlDbType.Int).Value=stuID;

connection.Open();
result=objCommand.ExecuteNonQuery();
}
returnresult;

}
#endregion

publicintInsertStudent(Studentmodel)
{

intresult=0;
SqlConnectionconnection=newSqlConnection(connString);
//构建插入的sql语句
stringsql=string.Format("INSERTINTOStudent(stuName,age)values('{0}','{1}')",
model.StuName,model.Age);
//定义command对象
SqlCommandcommand=newSqlCommand(sql,connection);

try
{
connection.Open();
result=command.ExecuteNonQuery();//执行命令

}
catch(Exceptionex)
{

Console.WriteLine(ex.Message);
}
finally
{
connection.Close();
}

returnresult;
}

publicintInsertStudent2(Studentmodel)
{

intresult=0;
//构建插入的sql语句
stringsql="INSERTINTOStudent(age,stuName)values(@age,@stuName)";
using(SqlConnectionconnection=newSqlConnection(connString))
{
SqlCommandobjCommand=newSqlCommand(sql,connection);

objCommand.Parameters.Add("@age",SqlDbType.Int).Value=model.Age;
objCommand.Parameters.Add("@stuName",SqlDbType.NVarChar,50).Value=model.StuName;

connection.Open();
result=objCommand.ExecuteNonQuery();
}
returnresult;
}

publicintInsertStudent3(Studentmodel)
{
intresult=0;
using(SqlConnectionconnection=newSqlConnection(connString))
{
SqlCommandobjCommand=newSqlCommand(dboOwner+".usp_InsertStudent",connection);
objCommand.CommandType=CommandType.StoredProcere;

objCommand.Parameters.Add("@age",SqlDbType.Int).Value=model.Age;
objCommand.Parameters.Add("@stuName",SqlDbType.NVarChar,50).Value=model.StuName;

connection.Open();
result=objCommand.ExecuteNonQuery();
}
returnresult;

}

publicintInsertStudent5(Studentmodel)
{
intoutputResult=0;
intreturnvalue=0;
using(SqlConnectionconnection=newSqlConnection(connString))
{
SqlCommandobjCommand=newSqlCommand(dboOwner+".usp_InsertStudent",connection);
objCommand.CommandType=CommandType.StoredProcere;

objCommand.Parameters.Add("@age",SqlDbType.Int).Value=model.Age;
objCommand.Parameters.Add("@stuName",SqlDbType.NVarChar,50).Value=model.StuName;
//定义输出参数
SqlParameterparameter=newSqlParameter("@stuID",SqlDbType.Int);
parameter.Direction=ParameterDirection.Output;
objCommand.Parameters.Add(parameter);

//定义ReturnValue参数
objCommand.Parameters.Add("ReturnValue",SqlDbType.Int);
objCommand.Parameters["ReturnValue"].Direction=ParameterDirection.ReturnValue;
connection.Open();
objCommand.ExecuteNonQuery();//执行命令
//获取输出参数的值在命令执行以后
outputResult=(int)objCommand.Parameters["@stuID"].Value;
//存储过程中为定义return值默认为0
returnvalue=(int)objCommand.Parameters["ReturnValue"].Value;
}
returnreturnvalue;

}

publicIListGetAllStudents1()
{

IListdataList=newList();
DataSetdataSet=newDataSet(); //声明并初始化DataSet
SqlDataAdapterdataAdapter; //声明DataAdapter

using(SqlConnectionconn=newSqlConnection(connString))
{
//定义command对象
SqlCommandcommand=newSqlCommand(dboOwner+".usp_SelectStudentsAll",conn);
command.CommandType=CommandType.StoredProcere;
//Command定义带参数的SQL语句的参数
//command.Parameters.Add("@stuID",SqlDbType.Int);
//给输入参数赋值
//command.Parameters["@stuID"].Value=5;
conn.Open();
//初始化DataAdapter
dataAdapter=newSqlDataAdapter(command);

//填充DataSet
dataAdapter.Fill(dataSet,"dataSetName");

//处理数据集中的数据
foreach(DataRowrowindataSet.Tables[0].Rows)
{
Studentmodel=newStudent();
model.StuId=Convert.ToInt32(row["stuID"]);
model.StuName=Convert.ToString(row["stuName"]);
dataList.Add(model);

}

}
returndataList;

}

publicvoidMoreResult()
{
DataSetdataSet=newDataSet(); //声明并初始化DataSet
SqlDataAdapterdataAdapter; //声明DataAdapter

//定义查询语句
stringsql=string.Format("SELECT*FROMstudentwherestuid>50;SELECT*FROMstudent");
SqlConnectionconnection=newSqlConnection(connString);
try
{
connection.Open();
//初始化DataAdapter
dataAdapter=newSqlDataAdapter(sql,connection);

//填充DataSet
dataAdapter.Fill(dataSet,"dataSetName");

//处理数据集中的数据
foreach(DataRowrowindataSet.Tables[0].Rows)
{
//intgradeId=(int)row["GradeID"];

}
}
catch(Exceptionex)
{

Console.WriteLine(ex.Message);
}
finally
{
connection.Close();
}

}

}
}

‘捌’ java中PreparedStatement类的setString用法

setString是定义了字符串中第n个”?“字符的替换。
举例：
string strsql = "select emp_id from employee where emp_id = ?";
preparedstatement pstmt = conn.preparestatement(strsql);
pstmt.setstring(1,"pma42628m");
解释：此时sql中的"?"的值就是”pma42628m“。
代码完整举例：
import java.sql.*;
public class mypreparedstatement {
private final string db_driver="com.microsoft.jdbc.sqlserver.sqlserverdriver";
private final string url = "jdbc:microsoft:sqlserver://127.0.0.1:1433;databasename=pubs";
public mypreparedstatement()
{
}
public void query() throws sqlexception{
connection conn = this.getconnection();
string strsql = "select emp_id from employee where emp_id = ?";
preparedstatement pstmt = conn.preparestatement(strsql);
pstmt.setstring(1,"pma42628m");
resultset rs = pstmt.executequery();

while(rs.next()){
string fname = rs.getstring("emp_id");
system.out.println("the fname is " + fname);
}
rs.close();
pstmt.close();
conn.close();
}
private connection getconnection() throws sqlexception{
// class.
connection conn = null;
try {
class.forname(db_driver);
conn = drivermanager.getconnection(url,"sa","sa");
}
catch (classnotfoundexception ex) {}
return conn;
}
//main
public static void main(string[] args) throws sqlexception {
mypreparedstatement jdbctest1 = new mypreparedstatement();
jdbctest1.query();
}
}

‘玖’ sqldatareader string 读取变成 数组的一个问题

你可以定义一个string数组用for循环给他赋值，这样你用的时候就方便点了
string sql = "select extra from EventExpand where Id="+eid;
private string[] row1;
row1=new string[];
for(int i=0;i<数组长度;i++)
{
try
{
using (SqlDataReader reader = DBHelper.GetReader(sql))
{
while (reader.Read())
{
row1[i]=reader["extra"].ToString().trim();
}
}
}
catch (Except
}

‘拾’ 如何在django shell中查看执行的数据库sql语句

C#中执行SQL语句//SQL查询语句publicDataTablequery(stringsql){//server=127.0.0.1;DataTabledt=newDataTable();//DataRowdr;stringconnString="server=127.0.0.1;uid=sa;pwd=;database=TJPTTC";SqlConnectionconn=newSqlConnection(connString);SqlDataAdapteradapter=newSqlDataAdapter(sql,conn);adapter.Fill(dt);returndt;}//SQL非查询语句publicvoidnoQuery(stringsql){//server=127.0.0.1;stringconnString="server=GLASSESONION;uid=sa;pwd=;database=TJPTTC";SqlConnectionconn=newSqlConnection(connString);SqlCommandcmd=newSqlCommand(sql,conn);conn.Open();cmd.ExecuteNonQuery();conn.Close();}