如何在Java的sqlite中从多个表中进行选择？

Question

我正在尝试学习如何在Java程序中使用sqlite数据库。（不是Android）。我转到此链接，下载了jdbc库并复制了示例。该示例工作无误。然后，我向数据库中添加了另一个表，并希望将两个表连接起来，并从每个表中选择一次列。我在从数据库进行查询的行上收到错误no such column: 'person.name'。我尝试了多种不同的方式来联接表和进行选择，但是每次我遇到异常时Table.columnName。有人可以告诉我正确的语法以在sqlite中联接两个表吗？这是我的代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Sample
{
  public static void main(String[] args) throws ClassNotFoundException
  {
    // load the sqlite-JDBC driver using the current class loader
    Class.forName("org.sqlite.JDBC");

Connection connection = null;
try
{
  // create a database connection
  connection = DriverManager.getConnection("jdbc:sqlite:newSample.db");
  Statement statement = connection.createStatement();
  statement.setQueryTimeout(30);  // set timeout to 30 sec.

  statement.executeUpdate("drop table if exists person");
  statement.executeUpdate("drop table if exists purchase");
  statement.executeUpdate("create table person (id integer, name string)");
  statement.executeUpdate("create table purchase (id integer, name string)");
  statement.executeUpdate("insert into purchase values(1, 'shampoo')");
  statement.executeUpdate("insert into purchase values(1, 'cheese')");
  statement.executeUpdate("insert into purchase values (2, 'cherries')");
  statement.executeUpdate("insert into purchase values (3, 'yogurt')");
  statement.executeUpdate("insert into purchase values (3, 'butter')");
  statement.executeUpdate("insert into person values(1, 'leo')");
  statement.executeUpdate("insert into person values(2, 'yui')");
  statement.executeUpdate("insert into person values(3, 'Steve')");
  ResultSet rs = statement.executeQuery("select purchase.name, person.name from 
  purchase inner join person on person.id = purchase.id"); <-- This is where I get the error!!

  while(rs.next())
  {
    // read the result set
    System.out.println("name = " + rs.getString("person.name"));
    System.out.println("id = " + rs.getInt("person.id"));
    System.out.println("purchase = " + rs.getString("purchase.name"));
  }
}
catch(SQLException e)
{
  // if the error message is "out of memory", 
  // it probably means no database file is found
  System.err.println(e.getMessage());
}
finally
{
  try
  {
    if(connection != null)
      connection.close();
  }
  catch(SQLException e)
  {
    // connection close failed.
    System.err.println(e);
  }
}

}}

Answer 1

在SQLite的文档说：

结果列的名称是该列的“ AS”子句的值（如果存在AS子句）。如果没有AS子句，则该列的名称未指定，并且可能从一个版本的SQLite更改为下一个版本。

您应该使用SQLite碰巧使用的列名：

rs.getString("name")

或为结果列指定一个唯一的名称：

executeQuery("select person.name AS person_name, ...")
rs.getString("person_name")

或者只使用列索引：

rs.getString(1)