Android SQLite添加列，保留数据_Android_Sqlite

Android SQLite添加列，保留数据

android sqlite

Android SQLite添加列，保留数据,android,sqlite,Android,Sqlite,我有一个包含4列的数据库： @Override public void onCreate(SQLiteDatabase database) { database.execSQL("CREATE TABLE " + DATABASENAME + " (name TEXT, latitude REAL, longitude REAL, country TEXT);"); } 现在我想添加另一列，但保留数据库中已有的行。我该怎么做？我找不到任何有用的参考资料 @Override pu

我有一个包含4列的数据库：

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

现在我想添加另一列，但保留数据库中已有的行。我该怎么做？我找不到任何有用的参考资料

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

编辑

我已将onCreate修改为：

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

我的责任是：

@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);
}

但是，现在我得到了这个stacktrace：

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

我没有使用过android，但sqlite像大多数SQL实现一样提供了“alter table”：

有关在表上创建新列的语法，请参见第页。基本上是：

ALTER TABLE mytable ADD COLUMN mycolumn TEXT

在您的onUpgrade方法中，它看起来像这样：

@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);
}

更好的方法

@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");

    }
}

假设在案例1中，您升级到了db版本2。您创建了一个新表，但忘记了将在案例2中看到的myNewColumn。如果将db版本更改为3，则案例2将在从2升级到3时运行。

将新列添加到db的正确方法（例如在版本2中）是：

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

@覆盖
public void onUpgrade（SQLiteDatabase db，int-oldVersion，int-newVersion）{
如果（旧版本<2）{
execSQL（“ALTERTABLE mytable ADD COLUMN mycolumn TEXT”）；
}
}

它涵盖了所有陷阱，包括所选答案的主要问题：如果用户从版本1升级到版本3，他们将完全错过升级查询！这些用户将处于尴尬的境地，他们缺少一些中间更新，并且没有预期的sql模式

另外，不要忘记更改create语句添加新列。

ALTERTABLE MyTable ADD column MyNewCol TEXT；为什么之后要调用onCreate（）？升级意味着已经调用了onCreate（）（意味着已经创建了表/db）。异常中详细介绍了该问题（甚至包括onCreate（）中的行号-第25行）。您正在尝试创建一个已经存在的表。啊，好的。但是我有一行代码，在从版本1更新后删除db，我需要调用onCreate吗？否-不要调用onCreate（），去掉“else if（oldVersion==1）{…}”代码。现在，如果旧版本是2，新版本是3，那么它将更新您的表名。而且您似乎对数据库名和表名感到困惑。您说的是创建一个名为DATABASENAME的表。您不是在创建数据库，而是在数据库中创建一个表。在版本3中，不是第二次查询，而是案例3中的冗余查询。这是在onUpgrade上t显示旧版本为版本2时，因此新版本将为版本3并运行代码。此代码正确且有效。我看到此代码的唯一问题是您应该删除switch语句中的所有中断（并确保所有情况都按升序排列），以便旧版本案例下的所有案例也被执行。更新了我的答案。。谢谢@It从案例1中删除中断是不必要的，这是

onCreate

方法的工作。

onUpgrade

仅当新版本之前存在数据库时才会被调用，因此执行类似于以下内容的查询：

”创建表格（如果存在）“

将不起作用。