@jkschneiderの答えは正しいです。ただし、より良いアプローチがあります。
リンクhttps://riggaroo.co.za/android-sqlite-database-use-onupgrade-correctly/で説明されているように、各更新のsqlファイルに必要な変更を書き込みます
from_1_to_2.sql
ALTER TABLE books ADD COLUMN book_rating INTEGER;
from_2_to_3.sql
ALTER TABLE books RENAME TO book_information;
from_3_to_4.sql
ALTER TABLE book_information ADD COLUMN calculated_pages_times_rating INTEGER;
UPDATE book_information SET calculated_pages_times_rating = (book_pages * book_rating) ;
これらの.sqlファイルは、データベースのバージョンに応じてonUpgrade（）メソッドで実行されます。
DatabaseHelper.java
public class DatabaseHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 4;
private static final String DATABASE_NAME = "database.db";
private static final String TAG = DatabaseHelper.class.getName();
private static DatabaseHelper mInstance = null;
private final Context context;
private DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.context = context;
}
public static synchronized DatabaseHelper getInstance(Context ctx) {
if (mInstance == null) {
mInstance = new DatabaseHelper(ctx.getApplicationContext());
}
return mInstance;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(BookEntry.SQL_CREATE_BOOK_ENTRY_TABLE);
// The rest of your create scripts go here.
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.e(TAG, "Updating table from " + oldVersion + " to " + newVersion);
// You will not need to modify this unless you need to do some android specific things.
// When upgrading the database, all you need to do is add a file to the assets folder and name it:
// from_1_to_2.sql with the version that you are upgrading to as the last version.
try {
for (int i = oldVersion; i < newVersion; ++i) {
String migrationName = String.format("from_%d_to_%d.sql", i, (i + 1));
Log.d(TAG, "Looking for migration file: " + migrationName);
readAndExecuteSQLScript(db, context, migrationName);
}
} catch (Exception exception) {
Log.e(TAG, "Exception running upgrade script:", exception);
}
}
@Override
public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
private void readAndExecuteSQLScript(SQLiteDatabase db, Context ctx, String fileName) {
if (TextUtils.isEmpty(fileName)) {
Log.d(TAG, "SQL script file name is empty");
return;
}
Log.d(TAG, "Script found. Executing...");
AssetManager assetManager = ctx.getAssets();
BufferedReader reader = null;
try {
InputStream is = assetManager.open(fileName);
InputStreamReader isr = new InputStreamReader(is);
reader = new BufferedReader(isr);
executeSQLScript(db, reader);
} catch (IOException e) {
Log.e(TAG, "IOException:", e);
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
Log.e(TAG, "IOException:", e);
}
}
}
}
private void executeSQLScript(SQLiteDatabase db, BufferedReader reader) throws IOException {
String line;
StringBuilder statement = new StringBuilder();
while ((line = reader.readLine()) != null) {
statement.append(line);
statement.append("\n");
if (line.endsWith(";")) {
db.execSQL(statement.toString());
statement = new StringBuilder();
}
}
}
}
サンプルプロジェクトも同じリンクで提供されています：https : //github.com/riggaroo/AndroidDatabaseUpgrades