安卓数据库代码

import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "MyDatabase.db";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = "users";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_NAME = "name";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableQuery = "CREATE TABLE " + TABLE_NAME + " (" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_NAME + " TEXT)";
        db.execSQL(createTableQuery);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    public long insertUser(String name) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, name);
        return db.insert(TABLE_NAME, null, values);
    }

    public String getUser(int id) {
        SQLiteDatabase db = this.getReadableDatabase();
        String[] columns = {COLUMN_NAME};
        String selection = COLUMN_ID + " = ?";
        String[] selectionArgs = {String.valueOf(id)};
        Cursor cursor = db.query(TABLE_NAME, columns, selection, selectionArgs, null, null, null);
        if (cursor != null && cursor.moveToFirst()) {
            String name = cursor.getString(cursor.getColumnIndexOrThrow(COLUMN_NAME));
            cursor.close();
            return name;
        }
        return null;
    }
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion < 2) {
        // 添加新列或修改表结构
        db.execSQL("ALTER TABLE " + TABLE_NAME + " ADD COLUMN new_column TEXT");
    }
}

db.execSQL("CREATE INDEX idx_name ON " + TABLE_NAME + "(" + COLUMN_NAME + ")");