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SQLite добавить столбец, сохранить данные

У меня есть база данных с 4 столбцами:

@Override
public void onCreate(SQLiteDatabase database) {
        database.execSQL("CREATE TABLE " + DATABASENAME + " (name TEXT, latitude REAL, longitude REAL, country TEXT);");
}

Теперь я хочу добавить еще один столбец, но сохранить строки, которые уже находятся в базе данных. Как мне это сделать? Я не могу найти полезные ссылки на это.

@Override
public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {
    //What to do here?
}

ИЗМЕНИТЬ

Я изменил my onCreate на:

@Override
public void onCreate(SQLiteDatabase database) {
    database.execSQL("CREATE TABLE " + DATABASENAME + " (name TEXT, latitude REAL, longitude REAL, country TEXT, code TEXT);");
}

и мой onUpgrade для:

@Override
public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {
    Logger.log("Updating userstations database from " + arg1 + " to " + arg2 + ".");
    if (arg1 == 2 && arg2 == 3) {
        db.execSQL("ALTER TABLE " + DATABASENAME + " ADD COLUMN code TEXT;");
    } else if(arg1 == 1){
        db.execSQL("DROP TABLE IF EXISTS " + DATABASENAME);
    }
    onCreate(db);
}

Однако теперь я получаю этот стек:

10-01 21:24:19.581: ERROR/Database(21434): Failure 1 (table userstations already exists) on 0x19c378 when preparing 'CREATE TABLE userstations (name TEXT, latitude REAL, longitude REAL, country TEXT, code TEXT);'.
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434): Couldn't open userstations for writing (will try read-only):
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434): android.database.sqlite.SQLiteException: table userstations already exists: CREATE TABLE userstations (name TEXT, latitude REAL, longitude REAL, country TEXT, code TEXT);
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.database.sqlite.SQLiteDatabase.native_execSQL(Native Method)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1763)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.databases.UserStationsOpenHelper.onCreate(UserStationsOpenHelper.java:25)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.databases.UserStationsOpenHelper.onUpgrade(UserStationsOpenHelper.java:36)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:132)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:187)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.databases.UserStationsOpenHelper.getStations(UserStationsOpenHelper.java:43)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.Data.readUserStations(Data.java:369)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.Data.getUserStations(Data.java:210)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.stationstab.StationsActivity.newStations(StationsActivity.java:190)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.stationstab.StationsActivity.refresh(StationsActivity.java:129)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.stationstab.StationsActivity.onCreate(StationsActivity.java:108)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:1598)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.stationstab.StationsActivityGroup.onCreate(StationsActivityGroup.java:38)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:1598)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:654)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.widget.TabHost.setCurrentTab(TabHost.java:326)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.widget.TabHost.addTab(TabHost.java:216)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.TreinVerkeer.setupTab(TreinVerkeer.java:131)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.TreinVerkeer.initTabs(TreinVerkeer.java:108)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.myapp.myapp.TreinVerkeer.onCreate(TreinVerkeer.java:62)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.access$1500(ActivityThread.java:123)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.os.Looper.loop(Looper.java:123)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at android.app.ActivityThread.main(ActivityThread.java:3835)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at java.lang.reflect.Method.invokeNative(Native Method)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at java.lang.reflect.Method.invoke(Method.java:507)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
10-01 21:24:19.611: ERROR/SQLiteOpenHelper(21434):     at dalvik.system.NativeStart.main(Native Method)
10-01 21:24:19.621: DEBUG/AndroidRuntime(21434): Shutting down VM
10-01 21:24:19.621: WARN/dalvikvm(21434): threadid=1: thread exiting with uncaught exception (group=0x4018a560)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434): FATAL EXCEPTION: main
10-01 21:24:19.641: ERROR/AndroidRuntime(21434): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.myapp/com.myapp.myapp.TreinVerkeer}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.myapp/com.myapp.myapp.stationstab.StationsActivityGroup}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.myapp/com.myapp.myapp.stationstab.StationsActivity}: android.database.sqlite.SQLiteException: Can't upgrade read-only database from version 2 to 3: /data/data/com.myapp.myapp/databases/userstations
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.access$1500(ActivityThread.java:123)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.os.Looper.loop(Looper.java:123)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.main(ActivityThread.java:3835)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at java.lang.reflect.Method.invokeNative(Native Method)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at java.lang.reflect.Method.invoke(Method.java:507)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at dalvik.system.NativeStart.main(Native Method)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.myapp/com.myapp.myapp.stationstab.StationsActivityGroup}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.myapp/com.myapp.myapp.stationstab.StationsActivity}: android.database.sqlite.SQLiteException: Can't upgrade read-only database from version 2 to 3: /data/data/com.myapp.myapp/databases/userstations
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:1598)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:654)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.widget.TabHost.setCurrentTab(TabHost.java:326)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.widget.TabHost.addTab(TabHost.java:216)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.myapp.myapp.TreinVerkeer.setupTab(TreinVerkeer.java:131)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.myapp.myapp.TreinVerkeer.initTabs(TreinVerkeer.java:108)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.myapp.myapp.TreinVerkeer.onCreate(TreinVerkeer.java:62)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     ... 11 more
10-01 21:24:19.641: ERROR/AndroidRuntime(21434): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.myapp/com.myapp.myapp.stationstab.StationsActivity}: android.database.sqlite.SQLiteException: Can't upgrade read-only database from version 2 to 3: /data/data/com.myapp.myapp/databases/userstations
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:1598)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.myapp.myapp.stationstab.StationsActivityGroup.onCreate(StationsActivityGroup.java:38)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     ... 22 more
10-01 21:24:19.641: ERROR/AndroidRuntime(21434): Caused by: android.database.sqlite.SQLiteException: Can't upgrade read-only database from version 2 to 3: /data/data/com.myapp.myapp/databases/userstations
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:199)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.myapp.myapp.databases.UserStationsOpenHelper.getStations(UserStationsOpenHelper.java:43)
10-01 21:24:19.641: ERROR/AndroidRuntime(21434):     at com.myapp.myapp
4b9b3361

ОТВЕТЫ

Ответ 1

См. эту страницу для синтаксиса для создания нового столбца таблицы. В основном это:

ALTER TABLE mytable ADD COLUMN mycolumn TEXT

В вашем методе onUpgrade он будет выглядеть примерно так:

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    String upgradeQuery = "ALTER TABLE mytable ADD COLUMN mycolumn TEXT";
    if (oldVersion == 1 && newVersion == 2)
         db.execSQL(upgradeQuery);
}

Ответ 2

Лучший подход

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    switch (oldVersion) {
        case 1:
            db.execSQL(SQL_MY_TABLE);


        case 2:
            db.execSQL("ALTER TABLE myTable ADD COLUMN myNewColumn TEXT");

    }
}

Давайте скажем в случае 1, вы обновили версию db версии 2. Вы создали новую таблицу, но забыли myNewColumn, которую вы увидите в случае 2. Что это будет делать, если вы измените версию db на 3, в случае, если 2 если его обновление происходит от 2 до 3.

Ответ 3

Я не работал с android, но sqlite предоставляет "alter table", как это делает большинство реализаций SQL:

SQLite alter table

Ответ 4

Правильный способ добавить новый столбец в БД, например, в версии 2, будет выглядеть так:

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion < 2) {
         db.execSQL("ALTER TABLE mytable ADD COLUMN mycolumn TEXT");
    }
}

Он охватывает все подводные камни, включая серьезную проблему с выбранным ответом: если пользователь перейдет с версии 1 на 3, он полностью пропустит запрос на обновление! Эти пользователи окажутся в неловком подвешенном состоянии, где им не хватает нескольких промежуточных обновлений, и у них нет ожидаемой схемы sql.

Также не забудьте изменить оператор создания, добавив новый столбец.