Question

我想构建一个GPS数据库，其中每个表代表一次旅行。为此，必须通过按下按钮创建一个新表。

到目前为止，我已经完成了所有工作。

但是我希望根据这种模式显示表格： Trip_1; Trip_2; Trip_3 ......

但是我总是得到表名为null的错误消息。

android.database.sqlite.SQLiteException: near "Table": syntax error (code 1): , while compiling: CREATE TABLE Trip_ (ID INTEGER PRIMARY KEY, Table TEXT)

请帮我找错。

这是我的数据库类：

public class GPSDatabase extends SQLiteOpenHelper {

String TAG = "GPSDatabase";

int tnumber = 0;


public static GPSDatabase INSTANCE = null;

private static final String DB_NAME              = "eelo";
private static final int    VERSION              = 1;
public  static       String TABLE_NAME           = "Trip_0";
public  static final String TABLE_TRIP           = "Trip_";

public  static final String TABLE_COLUMN         = "Table";

public  static final String ID_COLUMN            = "ID";
public  static final String NUMBER_COLUMN        = "Number";
public  static final String DISTANCE_COLUMN      = "Distance";
public  static final String LATITUDE_COLUMN      = "Latitude";
public  static final String LONGITUDE_COLUMN     = "Longitude";


private GPSDatabase(Context context) {
    super(context, DB_NAME, null, VERSION);
}


public static GPSDatabase getInstance (final Context context){
    if (INSTANCE == null){
        INSTANCE = new GPSDatabase(context);
    }
    return INSTANCE;
}

@Override
public void onCreate(SQLiteDatabase db) {


    String createTripQuery =
                "CREATE TABLE " + TABLE_TRIP + " (" + ID_COLUMN + " INTEGER PRIMARY KEY, " + TABLE_COLUMN + " TEXT)";

    String createQuery;
    if (tnumber==0) {
        createQuery =
                "CREATE TABLE " + TABLE_NAME + " (" + ID_COLUMN + " INTEGER PRIMARY KEY, " + NUMBER_COLUMN + " INTEGER DEFAULT NULL, " + DISTANCE_COLUMN + " INTEGER DEFAULT NULL, " + LATITUDE_COLUMN + " REAL DEFAULT NULL, " + LONGITUDE_COLUMN + " REAL DEFAULT NULL)";
    }
    else{
        createQuery =
                "CREATE TABLE " + getTrip(tnumber) + " (" + ID_COLUMN + " INTEGER PRIMARY KEY, " + NUMBER_COLUMN + " INTEGER DEFAULT NULL, " + DISTANCE_COLUMN + " INTEGER DEFAULT NULL, " + LATITUDE_COLUMN + " REAL DEFAULT NULL, " + LONGITUDE_COLUMN + " REAL DEFAULT NULL)";
    }
    db.execSQL(createTripQuery);
    db.execSQL(createQuery);
    Log.d(TAG, "Table created");
    tnumber++;

}

在这里，我获得了新旅行的表名：

public String getTrip(final long id) {

    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.query(TABLE_TRIP, new String[]{ID_COLUMN, TABLE_COLUMN}, ID_COLUMN + " = ?", new String[]{String.valueOf(id)}, null, null, null);

    String table = null;

    if (cursor != null && cursor.getCount() > 0) {
        cursor.moveToFirst();

        table = cursor.getString(cursor.getColumnIndex(TABLE_COLUMN));

    }

    Log.d(TAG, "getTable: "+table);
    return table;
}

这是来自Main Activity的ONCLICK-Methode;

public static GPSDatabase db;
public static int tripNumber = 0;
public static boolean clicked=false;
int NAV = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {

...

    db = GPSDatabase.getInstance(this);

...

    Button btn= (Button)findViewById(R.id.button3);
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Log.d("new Trip ","clicked");
            tripNumber++;

            long newID = -1;

            try{
                SQLiteDatabase database = db.getWritableDatabase();

                ContentValues values = new ContentValues();

                values.put(db.TABLE_COLUMN, "Trip_"+tripNumber);

                newID = database.insert(db.TABLE_TRIP, null, values);

            }catch (SQLiteException e){
                Log.e(TAG,"insert");
            }finally {
                Log.d(TAG,"TableTrip insert with ID " + newID);
            }

            SQLiteDatabase db1;
            db1 = db.getWritableDatabase();
            db.TABLE_NAME = db.TABLE_TRIP+tripNumber;
            String dropTable = "DROP TABLE IF EXISTS " + (db.TABLE_NAME+(tripNumber-1));
            db1.execSQL(dropTable);
            String createQuery =
                    "CREATE TABLE " + db.TABLE_NAME + " (" + db.ID_COLUMN + " INTEGER PRIMARY KEY, " + db.NUMBER_COLUMN + " INTEGER DEFAULT NULL, " + db.DISTANCE_COLUMN + " INTEGER DEFAULT NULL, " + db.LATITUDE_COLUMN + " REAL DEFAULT NULL, " + db.LONGITUDE_COLUMN + " REAL DEFAULT NULL)";


            db1.execSQL(createQuery);
        }
    });
}

Answer 1

问题在于将列命名为mainTabBar中的表。 SQLite认为它遇到了关键字TABLE，这在语法上是错误的。

如果你真的想要一个名为Table的列，这是可能的，你可以使用public static final String TABLE_COLUMN = "Table";。但是，这可能仍然存在问题并且令人困惑。

您也可以使用public static final String TABLE_COLUMN = "'Table'";来避免使用推荐的（但相对很少使用）

SQLite会不时添加新的关键字特征。因此，为了防止您的代码被未来破坏增强功能，您通常应引用任何标识符英语单词，即使你没有。[强调补充]

SQLite Keywords

的更多信息

所以也许_yourcolumnname

但是，也许更好的解决方案是应用规范化（减少数据库冗余）并使用一个列来标识 trip ，而不是具有多个结构相同的表。< / p>

e.g。你可以使用： -

public  static final String TABLE_COLUMN         = "_Table";

然后，您只需要一个表创建语句，而private static final String DB_NAME = "eelo"; private static final int VERSION = 1; public static final String TABLE_TRIP = "Trip_"; public static final String ID_COLUMN = "ID"; public static final String NUMBER_COLUMN = "Number"; public static final String DISTANCE_COLUMN = "Distance"; public static final String LATITUDE_COLUMN = "Latitude"; public static final String LONGITUDE_COLUMN = "Longitude"; public static final String TRIP_COLUMN = "Trip";方法中没有逻辑，例如它可能是： -

onCreate

然后你不需要@Override public void onCreate(SQLiteDatabase db) { String createQuery = "CREATE TABLE " + TABLE_NAME + " (" + ID_COLUMN + " INTEGER PRIMARY KEY, " + NUMBER_COLUMN + " INTEGER DEFAULT NULL, " + DISTANCE_COLUMN + " INTEGER DEFAULT NULL, " + LATITUDE_COLUMN + " REAL DEFAULT NULL, " + LONGITUDE_COLUMN + " REAL DEFAULT NULL + TRIP_COLUMN + "INTEGER" + )"; } db.execSQL(createQuery); Log.d(TAG, "Table created"); }交换表，而只需要使用getTrip（注意int可能很长，所以很可能有足够的数字）来实现相同的最终结果。

通过方法创建具有连续数字的表

1 个答案: