Java向PostgreSQL发送prepared statement 与 libpq 向PostgreSQL发送prepared statement之比较：

Java 代码，在数据库端，并没有当成 prepared statetment 被处理。

C代码通过libpq 访问数据库端，被当成了 prepared statement 处理。也许是因PostgreSQL对JDBC的支持毕竟是后期出现的：

下面看代码和运行结果：

Java 代码：

import java.sql.*;
 
public class Test01 {
 
        public static void main(String argsv[]){
        try
         {
           Class.forName("org.postgresql.Driver").newInstance();
           String url = "jdbc:postgresql://localhost:5432/postgres" ;
   
           Connection con = DriverManager.getConnection(url,"postgres","postgres" );
          
           ///Phase 1:-------------Select data from table-----------------------
 
          
           System.out.println("Phase 1------------------------start");
          
           String strsql = " select * from customers where cust_id = ?";
           PreparedStatement pst=con.prepareStatement(strsql);
 
           pst.setInt(1,3); //find the customer with cust_id of 3.
          
           ResultSet rs = pst.executeQuery();
          
           while (rs.next())
            {
               System.out.print("cust_id:"+rs.getInt( "cust_id"));
               System.out.println("...cust_name:"+rs.getString( "cust_name" ));
           }
           System.out.println("Phase 1------------------------end\n");
          
          
          
           ///Phase 2:-------------Use connection again,to select data from data dictionary-----------------------
          
           System.out.println("Phase 2------------------------start");
          
           strsql = "select * from pg_prepared_statements";
           pst=con.prepareStatement(strsql);          
          
           rs = pst.executeQuery();
          
           while (rs.next())
           {
              System.out.println("statement:"+rs.getString( "statement"));
           }          
           System.out.println("Phase 2------------------------end\n");          
          
           ///Phase 3:-------------Use connection again,to select data from table-----------------------
 
           System.out.println("Phase 3------------------------start");          
           strsql = "select * from customers";
           pst=con.prepareStatement(strsql);          
          
           rs = pst.executeQuery();
          
           while (rs.next())
           {
              System.out.print("cust_id:"+rs.getInt( "cust_id"));
              System.out.println("...cust_name:"+rs.getString( "cust_name" ));
          }           
         
          System.out.println("Phase 3------------------------end\n");           
          
          rs.close();          
          pst.close();
          con.close();
          
       }
        catch (Exception ee)
        {
           System.out.print(ee.getMessage());
       }
        }
 
}

更多相关文章

随机推荐