Android sqlite数据库列错误

Question

我在应用程序中插入sqlite数据库时遇到问题。 每当我尝试插入数据时，都会出现以下错误：android.database.sqlite.SQLiteException：表tblstudents没有名为Town的列。 我尝试浏览代码，但无法理解是什么导致了此错误。 我的代码如下：

package com.StudentTracker;
import java.sql.Blob;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;


public class DBAdapter {

    public static final String KEY_ROWID = "id";
    public static final String KEY_STUDENTNAME = "studentname";
    public static final String KEY_DOB = "dob";
    public static final String KEY_ADDRESS1 = "address1";
    public static final String KEY_ADDRESS2 = "address2";
    public static final String KEY_TOWN = "town";
    public static final String KEY_POSTCODE = "postcode";
    public static final String KEY_PHONE = "phone";  
    public static final String KEY_STUDENT_PIC = "studentpic";  

    private static final String TAG = "DBAdapter"; 



    private static final String DATABASE_NAME = "studentDB2";
    private static final String DATABASE_TABLE = "tblstudents";
    private static final int DATABASE_VERSION = 1;

    private static final String DATABASE_CREATE =
        "create table tblstudents (id integer primary key autoincrement, "
        + "studentname text not null, dob text not null, " 
        + "address1 text not null, address2 text not null, "
        + "town text not null, postcode text not null, "
        + " phone text not null);";

    private final Context context; 

    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;

    public DBAdapter(Context ctx) 
    {
        this.context = ctx;
        DBHelper = new DatabaseHelper(context);
    }

    private static class DatabaseHelper extends SQLiteOpenHelper 
    {
        DatabaseHelper(Context context) 
        {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) 
        {
            db.execSQL(DATABASE_CREATE);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, 
        int newVersion) 
        {
            Log.w(TAG, "Upgrading database from version " + oldVersion 
                    + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS studentDB2");
            onCreate(db);
        }
    }    

    //---opens the database---
    public DBAdapter open() throws SQLException 
    {
        db = DBHelper.getWritableDatabase();
        return this;
    }

    //---closes the database---    
    public void close() 
    {
        DBHelper.close();
    }

    //---insert a title into the database---
    public long insertStudent(String studentname, String dob, String address1, String address2, String town, String postcode, String phone) 
    {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_STUDENTNAME, studentname);
        initialValues.put(KEY_DOB, dob);
        initialValues.put(KEY_ADDRESS1, address1);
        initialValues.put(KEY_ADDRESS2, address2);
        initialValues.put(KEY_TOWN, town);
        initialValues.put(KEY_POSTCODE, postcode);
        initialValues.put(KEY_PHONE, phone);
        //initialValues.put(KEY_STUDENT_PIC, studentpic);

        return db.insert(DATABASE_TABLE, null, initialValues);
    }

    //---deletes a particular title---
    public boolean deleteTitle(long rowId) 
    {
        return db.delete(DATABASE_TABLE, KEY_ROWID + 
                "=" + rowId, null) > 0;
    }

    //---retrieves all the titles---
    public Cursor getAllStudents() 
    {
        return db.query(DATABASE_TABLE, new String[] {
                KEY_ROWID, 
                KEY_STUDENTNAME,
                KEY_DOB,
                KEY_ADDRESS1,
                KEY_ADDRESS2,
                KEY_TOWN,
                KEY_POSTCODE,
                KEY_PHONE
                            }, 
                null, 
                null, 
                null, 
                null, 
                null);
    }

    //---retrieves a particular title---
    public Cursor getStudent(long rowId) throws SQLException 
    {
        Cursor mCursor =
                db.query(true, DATABASE_TABLE, new String[] {
                        KEY_ROWID, 
                        KEY_STUDENTNAME,
                        KEY_DOB,
                        KEY_ADDRESS1,
                        KEY_ADDRESS2,
                        KEY_TOWN,
                        KEY_POSTCODE,
                        KEY_PHONE                  
                        }, 
                        KEY_ROWID + "=" + rowId, 
                        null,
                        null, 
                        null, 
                        null, 
                        null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    //---updates a title---
    public boolean updateStudent(long rowId, String studentname, 
    String dob, String address1, String address2, String town,
    String postcode, String phone) 
    {
        ContentValues args = new ContentValues();
        args.put(KEY_STUDENTNAME, studentname);
        args.put(KEY_DOB, dob);
        args.put(KEY_ADDRESS1, address1);
        args.put(KEY_ADDRESS2, address2);
        args.put(KEY_TOWN, town);
        args.put(KEY_POSTCODE, postcode);
        args.put(KEY_PHONE, phone);
        //args.put(KEY_STUDENT_PIC, studentpic);

        return db.update(DATABASE_TABLE, args, 
                         KEY_ROWID + "=" + rowId, null) > 0;
    }




}

Answer 1

您应该将表tblstudents在OnUpgrade() ，而不是studentDB2表中。

db.execSQL("DROP TABLE IF EXISTS tblstudents");

不要忘记增加DATABASE_VERSION的数量。 否则，将不会调用OnUpgrade() 。

private static final int DATABASE_VERSION = 2;

Answer 2

public class DBaseHelper extends SQLiteOpenHelper {
private final static int    DB_VERSION = 2;

//检查它^^数据库版本是一个新值（已递增）

public TracksDB(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
}


@Override
public void onCreate(SQLiteDatabase db) {
    final String DATABASE_CREATE =
        "create table tblstudents (id integer primary key autoincrement, "
        + "studentname text not null, dob text not null, " 
        + "address1 text not null, address2 text not null, "
        + "town text not null, postcode text not null, "
        + " phone text not null);";
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion < 2) {
        final String ALTER_TBL = 
            "ALTER TABLE " + TABLE_NAME +
            " ADD COLUMN town text not null;";
        db.execSQL(ALTER_TBL);
    }
}
}

一旦增加了版本号，它将通知数据库构建器要注意onCreate方法中的create table语句。 一旦发现新内容或任何类型的差异，它将转到onUpgrade方法并运行所需的代码以使其按预期运行，现在包括表列。

Answer 3

如果您最近添加了该列，请记住也要增加数据库版本，以便执行升级例程。