java - Derby 架构错误

Question

我正在尝试将数据插入我的桌面应用程序的 Derby 嵌入式数据库。但是 Derby 给了我架构未找到错误的错误。我尝试通过根据用户名创建架构来解决错误，但没有解决我的问题。我搜索了互联网，但没有一个解决方案解决了我的问题。

package derbyd.ui;

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


public class AddStudent extends javax.swing.JFrame {

private void bt_saveActionPerformed(java.awt.event.ActionEvent evt) {                                        
    String conURL = "jdbc:derby:myDB;create=true";
    String user = "SOURABH";
    String passwd = "pass";
    Connection con = null;
    Statement st = null;
    String query;
    ResultSet rs = null;
    try
    {
        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
        con = DriverManager.getConnection(conURL, user, passwd);
        st = con.createStatement();
        System.out.println("Connection established");
        query = "INSERT INTO SOURABH.MyTable VALUES('"+txt_name.getText()+"','"+txt_surname.getText()+"')";
        st.executeUpdate(query);
        System.out.println("Added Successfully");
    }
    catch(Exception e)
    {
        System.out.println("Error ->"+e);
    }
}                                       


}

Answer 1

根据Frequently Asked Questions的 Apache Derby，您会看到:

A schema is only created by CREATE SCHEMA or creating an object (table etc.) in that schema (this is implicit schema creation).

在代码中，您需要先创建表，然后才能正常工作。

Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
con = DriverManager.getConnection(conURL, user, passwd);
st = con.createStatement();
System.out.println("Connection established");

st.executeUpdate("CREATE TABLE MyTable" +
        "(name VARCHAR(255), surname varchar(255))");
System.out.println("Table created");

query = "INSERT INTO SOURABH.MyTable VALUES(" +
        "'" + txt_name.getText() + "','" + txt_surname.getText() + "')";
st.executeUpdate(query);
System.out.println("Added Successfully");

输出为:

Connection established
Table created
Added Successfully

如果多次运行此语句，您将收到错误，因为该表已存在。为了解决这个问题，here .