Question

public class MyDBHandler extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "winkelskortrijk.db";
    private static final String TABLE_USERS = "users";
    private static final String TABLE_FAVOURITES = "favorieten";

    public static final String COLUMN_ID = "id";
    public static final String COLUMN_USERNAME = "username";
    public static final String COLUMN_PASSWORD = "password";

    public static final String COLUMN_ID2 = "id2";
    public static final String COLUMN_NAME = "naam";
    public static final String COLUMN_STRAAT = "straat";
    public static final String COLUMN_HUISNR = "nr";
    public static final String COLUMN_POSTCODE = "postcode";
    public static final String COLUMN_DEELGEMEENTE = "deelgemeente";
    public static final String COLUMN_GEMEENTE = "gemeente";
    public static final String COLUMN_ADRES = "adres";

    public MyDBHandler(Context context, String name,
                       SQLiteDatabase.CursorFactory factory, int version) {
        super(context, DATABASE_NAME, factory, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String CREATE_USERS_TABLE = "CREATE TABLE " +
                TABLE_USERS + "("
                + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
                + COLUMN_USERNAME + " TEXT,"
                + COLUMN_PASSWORD + " TEXT"
                + ")";
        db.execSQL(CREATE_USERS_TABLE);

        String CREATE_FAVOURITES_TABLE = "CREATE TABLE " +
                TABLE_FAVOURITES + "("
                + COLUMN_ID2 + " INTEGER PRIMARY KEY,"
                + COLUMN_NAME + " TEXT,"
                + COLUMN_STRAAT + " TEXT,"
                + COLUMN_HUISNR + " INTEGER,"
                + COLUMN_POSTCODE + " INTEGER,"
                + COLUMN_DEELGEMEENTE + " TEXT,"
                + COLUMN_GEMEENTE + " TEXT,"
                + COLUMN_ADRES + " TEXT,"
                + COLUMN_ID + " INT, "
                + "FOREIGN KEY(" + COLUMN_ID + ") REFERENCES "
                + TABLE_USERS + "(id) " + ")";
        db.execSQL(CREATE_FAVOURITES_TABLE);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion,
                          int newVersion) {

    }


    public User findUser(User user) {

        String selectQuery = "SELECT  * FROM " + TABLE_USERS + " WHERE "
                + COLUMN_USERNAME + " = " + user.getUsername();

        SQLiteDatabase db = this.getWritableDatabase();

        Cursor cursor = db.rawQuery(selectQuery, null);

        User findUser = new User();

        if (cursor.moveToFirst()) {
            cursor.moveToFirst();
            findUser.setUserName(cursor.getString(1));
            findUser.setPassword(cursor.getString(2));
            cursor.close();
        } else {
            findUser = null;
        }
        db.close();
        return findUser;

    }

}

当我尝试运行findUser(User user)方法时，我得到一个SQLException没有这样的列：Gebruikersnaam（注意：Gebruikersnaam是user.getUserName（）中的变量，我希望此函数返回用户，如果它是发现或在没有的时候为空。

我做错了什么，是否有更好的方法来使用查询？

崩溃日志：

07-25 15：22：42.345 32264-32264 / com.example.hoofdgebruiker.winkelskortrijk E / AndroidRuntime：致命异常：主要过程：com.example.hoofdgebruiker.winkelskortrijk，PID：32264 android.database.sqlite.SQLiteException：没有这样的列： Gebruikersnaam（代码1）:,同时编译：SELECT * FROM users WHERE username = Gebruikersnaam 在 android.database.sqlite.SQLiteConnection.nativePrepareStatement（母语方法）在 android.database.sqlite.SQLiteConnection.acquirePreparedStatement（SQLiteConnection.java:887）在 android.database.sqlite.SQLiteConnection.prepare（SQLiteConnection.java:498）在 android.database.sqlite.SQLiteSession.prepare（SQLiteSession.java:588）在android.database.sqlite.SQLiteProgram。（SQLiteProgram.java:58）在android.database.sqlite.SQLiteQuery。（SQLiteQuery.java:37）在 android.database.sqlite.SQLiteDirectCursorDriver.query（SQLiteDirectCursorDriver.java:44）在 android.database.sqlite.SQLiteDatabase.rawQueryWithFactory（SQLiteDatabase.java:1316）在 android.database.sqlite.SQLiteDatabase.rawQuery（SQLiteDatabase.java:1255）在 com.example.hoofdgebruiker.winkelskortrijk.Database.MyDBHandler.findUser（MyDBHandler.java:78）在 com.example.hoofdgebruiker.winkelskortrijk.Homepage.MainActivity.register（MainActivity.java:49）在 com.example.hoofdgebruiker.winkelskortrijk.Homepage.Register $ 1.onClick（Register.java:47）在android.view.View.performClick（View.java:5198）在android.view.View $ PerformClick.run（View.java:21147）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:148）在android.app.ActivityThread.main（ActivityThread.java:5417） at java.lang.reflect.Method.invoke（Native Method）在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:726）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616）

Answer 1

只需更新查询

String selectQuery = "SELECT  * FROM " + TABLE_USERS + " WHERE "
            + COLUMN_USERNAME + " = " + user.getUsername();

到

String selectQuery = "SELECT  * FROM " + TABLE_USERS + " WHERE "
            + COLUMN_USERNAME + " = '" + user.getUsername()+"'";

将user.getUsername（）值括在单引号中，因为您将COLUMN_USERNAME定义为文本。如果您的字符串已包含引号，则它不起作用。在添加user.getUsername（）以查询从用户名中删除引号之前，如下所示

user.getUsername（）替换（ “\”“， ” ''“）;

Answer 2

你的问题在这里：

String selectQuery = "SELECT  * FROM " + TABLE_USERS + " WHERE "
        + COLUMN_USERNAME + " = " + user.getUsername();

由于user.getUsername()是文字，您必须执行以下操作：

String selectQuery = "SELECT  * FROM " + TABLE_USERS + " WHERE "
        + COLUMN_USERNAME + " = '" + user.getUsername() + "'";

干杯

获取SQLiteException：没有这样的列

2 个答案: