结果集开始前的 MySQL | 结果集开始前的

本文介绍了结果集开始前的 MySQL的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我试图从一个表中获取 personID 并在第二个表中使用它，然后从第二个表，但是我收到错误 列索引超出范围，3 .订单表由 3 列组成.

I am trying to get the personID from one table and use it in the second table, and the print each column value fromthe second table, however I am getting an the error column index out of range, 3 < 1. The order table consist of 3 columns.

public void getPersonsOrders(String firstName){
    Connection con = connect();
    try{
        Statement s = con.createStatement();
        s.executeUpdate("use stl;");
        ResultSet rs1 = s.executeQuery("select personID from person where first_name = " +"'"+firstName+"'"+";");       //get persons ID no.
        rs1.next();
        ResultSet rs2 = s.executeQuery("select * from orderr where personID = "+rs1.getInt(3)+";");             //use ID no. to
        for(int i = 1; i < 4; i++){                                                                             //retrive order
            System.out.println(rs2.getInt(i));
        }
    }
    catch(SQLException e){
        System.out.println("3" +e.getMessage());
    }
}

`推荐答案`

rs1 中只有一列返回，因此你应该使用 rs1.getInt(1).

There is only one column returned in rs1, therefore you should use rs1.getInt(1).

另一方面，这应该可以使用连接轻松解决:

On the other hand, this should easily be solved using a join:

SELECT o.* FROM order o
LEFT JOIN person p
ON p.personID = o.personID

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