Java Oracle jdbc SELECT语句

问题描述

我正在Eclipse环境中使用Java练习Oracle JDBC.我了解了如何通过使用next()迭代表的每一行来输出SELECT * from product.我在努力输出语句

I am practising Oracle JDBC using java in Eclipse environment. I understood how to output SELECT * from product by iterating each line of table using next() . I am stugglingTo output the statement

SELECT pid, pname
from product
where price>20

这是我的代码:

import java.sql.*;


public class intro {

    /**
     * @param args
     */
    public static void main(String[] args)
    {
    //  throws SQLException

        //initiazlie the connection

        Connection con=null;

        try //try connection to database
        {
            //load driver
            Class.forName("oracle.jdbc.OracleDriver");
            System.out.println("Oracle JDBC driver loaded ok.");
            con=DriverManager.getConnection("jdbc:oracle:thin:test/123321@localhost:1521:orcl");
            System.out.println("Connect with @oracle:1521:orcl");

            //declaring statement
            Statement stmt = con.createStatement();

            String dropProductTable="drop table product cascade constraints";

            //create string
            String createProductTable="CREATE TABLE product(" +
             "pid number," +
             "pname CHAR(20)," +
             "price number," +
             "PRIMARY KEY (pid)" +
             ")"; //do not add the semicolon(;) after closing the parenthesis.


            /*drop table */
            stmt.executeUpdate(dropProductTable);


            //execute the create statement
            stmt.executeUpdate(createProductTable);//execure the create statement

            //create string that holds the insert statement
            String insertIntoProduct="INSERT INTO product VALUES (1,'Pepsi',10)";
            String insertIntoProduct1="INSERT INTO product VALUES (2,'Fanta',20)";
            String insertIntoProduct2="INSERT INTO product VALUES (3,'Mirinda',30)";
            String insertIntoProduct3="INSERT INTO product VALUES (4,'Gum',5)";
            String updatePrice="UPDATE product set price=55 where price=20";



            //stmt.executeUpdate(insertIntoProduct);
            stmt.executeUpdate(insertIntoProduct);
            stmt.executeUpdate(insertIntoProduct1);
            stmt.executeUpdate(insertIntoProduct2);
            stmt.executeUpdate(insertIntoProduct3);

           //update statement
            stmt.executeUpdate(updatePrice);



            //save the select statement in a string
            String selectStat="SELECT * FROM product";
            String selectProduct="SELECT pid, pname from product where price>20";
            //stmt.executeUpdate(selectStat);

            //create a result set
            ResultSet rows = stmt.executeQuery(selectStat);
            ResultSet rows1= stmt.executeQuery(selectProduct);

            //stmt.executeQuery(selectStat);


            int count=0;
            while (rows.next()) {
                count+=1;
                String productNumber = rows.getString("pid");
                String productName = rows.getString("pname");
                String productPrice = rows.getString("price");
                System.out.println("Row #:"+count);
                System.out.println("Product#: "+productNumber);
                System.out.println("Product Name: "+productName);
                System.out.println("Price: "+productPrice);

                }

            int count1=0;
            while (rows1.next()) {
                count1+=1;
                String productNumber = rows1.getString("pid");
                String productName = rows1.getString("pname");
                String productPrice = rows1.getString("price");
                System.out.println("Row #:"+count);
                System.out.println("Product#: "+productNumber);
                System.out.println("Product Name: "+productName);
                System.out.println("Price: "+productPrice);

                }

            con.close();

        }
                catch (Exception e)
                {
                    System.err.println("Exception:"+e.getMessage());
                }


        }

    }

当我尝试输出selectProduct变量时，出现此错误

when I am trying to ouput selectProduct variable i got this error

Exception:Invalid column name

请寻求帮助

这是我得到的输出

Oracle JDBC driver loaded ok.
Connect with @oracle:1521:orcl
Row #:0
Product#: 2
Product Name: Fanta
Price: 55
Row #:0
Product#: 3
Product Name: Mirinda
Price: 30

推荐答案

在您的SELECT中，您只会得到"pid"和"pname":

In your SELECT you are only getting "pid" and "pname":

String selectProduct="SELECT pid, pname from product...

但是随后您尝试使用不在SELECT中的字段:

But then you're trying to use a field that isn't in your SELECT:

String productPrice = rows1.getString("price");

尝试在您的SELECT子句中添加价格".

Try putting "price" in your SELECT clause.

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