代码入下
import java .sql.*;public class PreparedStatementDemo01 {
public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
public static final String DBURL = "jdbc:mysql://localhost:3306/mumu" ;
public static final String DBUSER = "root" ;
public static final String DBPASS = "mysqladmin" ;
public static void main(String args[]) throws Exception{
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null;
String sql="select ?,? from mumu";
Class.forName(DBDRIVER);
conn=DriverManager.getConnection(DBURL, DBUSER, DBPASS);
ps=conn.prepareStatement(sql);
ps.setString(1, "name");
ps.setString(2, "password");
rs=ps.executeQuery();
while(rs.next()){
String name=rs.getString(1);
String word=rs.getString(2);
System.out.println(name+" "+word);
}
rs.close();
ps.close();
conn.close();
}
}
运行的结果如下:
name password
name password
name password
表的结构如下:
字段 id name password
import java .sql.*;public class PreparedStatementDemo01 {
public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
public static final String DBURL = "jdbc:mysql://localhost:3306/mumu" ;
public static final String DBUSER = "root" ;
public static final String DBPASS = "mysqladmin" ;
public static void main(String args[]) throws Exception{
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null;
String sql="select ?,? from mumu";
Class.forName(DBDRIVER);
conn=DriverManager.getConnection(DBURL, DBUSER, DBPASS);
ps=conn.prepareStatement(sql);
ps.setString(1, "name");
ps.setString(2, "password");
rs=ps.executeQuery();
while(rs.next()){
String name=rs.getString(1);
String word=rs.getString(2);
System.out.println(name+" "+word);
}
rs.close();
ps.close();
conn.close();
}
}
运行的结果如下:
name password
name password
name password
表的结构如下:
字段 id name password
在来看sql语句,select ?,? from mumu 通过pst设置两个问号的值后
sql语句会变成 select 'name','password' from mumu这时查的就不是name,password的字段,而是字符串'name','password'。
要查找name,password你只能用这样的sql语句:select name,password from mumu.不能通过PrepareStatement来设置列名,pst.setXXX()一般是用来设置where后面的条件的值
如:select * from mumu where name=? and password=? 这时才可以用ps来设值
public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
public static final String DBURL = "jdbc:mysql://localhost:3306/mumu" ;
public static final String DBUSER = "root" ;
public static final String DBPASS = "mysqladmin" ;
public static void main(String args[]) throws Exception{
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null; String sql="select name,password from mumu"; Class.forName(DBDRIVER);
conn=DriverManager.getConnection(DBURL, DBUSER, DBPASS);
ps=conn.prepareStatement(sql);
rs=ps.executeQuery(); while(rs.next()){
String name=rs.getString(1);
String word=rs.getString(2);
System.out.println(name+" "+word);
} rs.close();
ps.close();
conn.close(); }
}修改SQL语句,这样可以查询表内的内容。
加where条件,可以使用“???”
ps.setString(2, "password"); 这里name 与 password 是你要查询的字段 这样。setXXX()不能使用的