游标返回错误的值-sqlite-Android

Question

我正在开发一个短信应用程序，我试图从每次对话中获取最新的短信。

这是我的SQL语句：

SELECT MAX(smsTIMESTAMP) AS smsTIMESTAMP,_id, smsID, smsCONID, smsMSG, smsNUM, smsREAD, smsTYPE, smsSHORTMSG, COUNT(*) AS smsNUMMESSAGES FROM sms GROUP BY smsCONID ORDER BY smsTIMESTAMP desc

我在SQLite Expert中运行了查询，并且得到了正确的响应：

但是，当我在应用程序中运行它时，我得到：

这是我的桌子

这是我的Datamanipulator类：

public class DataManipulator {
    private static final  String DATABASE_NAME = "smsapplication.db";
    private static final int DATABASE_VERSION = 3;
    static final String TABLE_NAME = "sms";
    private static Context context;
    static SQLiteDatabase db;
    private static DataManipulator instance;

    private SQLiteStatement insertStmt;

    private static final String INSERT = "insert or ignore into "
        + TABLE_NAME + " (smsID, smsCONID, smsMSG, smsNUM, smsREAD, smsTIMESTAMP, smsTYPE, smsSHORTMSG) values (?,?,?,?,?,?,?,?)";

    public DataManipulator(Context context) {
        DataManipulator.context = context;
        OpenHelper openHelper = new OpenHelper(DataManipulator.context);
        DataManipulator.db = openHelper.getWritableDatabase();
        this.insertStmt = DataManipulator.db.compileStatement(INSERT);
    }
    public static DataManipulator getInstance(Context mContext)
    {
        if(instance == null)
        {
            instance = new DataManipulator(mContext);
        }
        return instance;
    }
    public long insert(int smsID, int smsCONID, String smsMSG,
            String smsNUM, int smsREAD, long smsTIMESTAMP, String smsTYPE, String smsSHORTMSG) {
        this.insertStmt.bindLong(1, smsID);
        this.insertStmt.bindLong(2, smsCONID);
        this.insertStmt.bindString(3, smsMSG);
        this.insertStmt.bindString(4, smsNUM);
        this.insertStmt.bindLong(5, smsREAD);
        this.insertStmt.bindString(6, String.valueOf(smsTIMESTAMP));
        this.insertStmt.bindString(7, smsTYPE);
        this.insertStmt.bindString(8, smsSHORTMSG);
        return this.insertStmt.executeInsert();
    }

    public void deleteAll() {
        db.delete(TABLE_NAME, null, null);
    }

    public Cursor getLastSmsForAllConversations()
    {
        Cursor cursor = db.query(TABLE_NAME, new String[] {"_id"," MAX(smsTIMESTAMP) AS smsTIMESTAMP ", "smsCONID", "smsNUM", "smsREAD", "smsTYPE","smsSHORTMSG","COUNT(*) AS smsNUMMESSAGES"  },
                null, null, "smsCONID", null, "smsTIMESTAMP desc"); 
        return cursor;
    }
    public Cursor getConversationMessages(int conID)
    {
        Cursor cursor = db.query(TABLE_NAME, new String[] {"_id", "smsID", "smsCONID", "smsMSG", "smsNUM", "smsREAD", "smsTIMESTAMP", "smsTYPE","smsSHORTMSG"  },
                "smsCONID="+conID, null, null, null, "smsTIMESTAMP asc"); 
        return cursor;
    }
    public void printCursor()
    {
        Cursor cursor = db.rawQuery("SELECT MAX(smsTIMESTAMP) AS smsTIMESTAMP,_id, smsID, smsCONID, smsMSG, smsNUM, smsREAD, smsTYPE, smsSHORTMSG, COUNT(*) AS smsNUMMESSAGES FROM sms GROUP BY smsCONID ORDER BY smsTIMESTAMP desc", null);

            //  db.query(TABLE_NAME, new String[] {"_id","smsTIMESTAMP AS smsTIMESTAMP ", "smsCONID", "smsNUM", "smsREAD", "smsTYPE","smsSHORTMSG"  },"smsCONID=40", null, null, null, "smsTIMESTAMP desc");  
        if (cursor.moveToFirst()){
               do{
                  String data ="";
                  data= cursor.getString(cursor.getColumnIndex("smsTIMESTAMP"))+" - " +cursor.getString(cursor.getColumnIndex("smsSHORTMSG"));
                  Log.i("data", data);
               }while(cursor.moveToNext()); 
            }
            cursor.close();
    }

    private static class OpenHelper extends SQLiteOpenHelper {

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

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL("CREATE TABLE " + TABLE_NAME + " (_id INTEGER , smsID INTEGER PRIMARY KEY, smsCONID INTEGER, smsMSG TEXT,smsNUM TEXT, smsREAD INTEGER, smsTIMESTAMP INTEGER, smsTYPE TEXT, smsSHORTMSG TEXT)");
        }

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

            if (db != null)
                db.close();

            super.close();

            }
    } 
}

Answer 1

使用时GROUP BY，结果的每一行对应于原始表的多行。这些结果的计算有三种可能性：

• 具有聚合函数的列类似于MAX或COUNT计算组中所有行的值；
• GROUP BY子句中出现的列只是从组中的 任何 记录中获取的（因为该组中的所有记录对该列具有相同的值）；
• 其他列是一个问题，因为组中的行可能具有不同的值。在标准SQL中，禁止使用此类列。SQLite允许使用它们，但是只为您提供组中任何随机行的值，而这几乎从来不是您想要的。从SQLite 3.7.11开始，您从与aMIN或MAX;匹配的行中获取值。这是您在SQLite Exprert中看到的，但在具有较旧SQLite的Android上却没有。

要解决您的问题，您必须首先使用aGROUP BY获取足够的信息以标识所需的记录：

SELECT smsCONID,                            -- OK: used in GROUP BY
       MAX(smsTIMESTAMP) AS smsTIMESTAMP,   -- OK: aggregate MAX
       COUNT(*) AS smsNUMMESSAGES           -- OK: aggregate COUNT
FROM sms
GROUP BY smsCONID
ORDER BY smsTIMESTAMP DESC

然后，将该结果表与原始sms表连接起来以获取这些记录的其他列：

SELECT *
FROM (SELECT smsCONID,
             MAX(smsTIMESTAMP) AS smsTIMESTAMP,
             COUNT(*) AS smsNUMMESSAGES
      FROM sms
      GROUP BY smsCONID) AS grouped
     JOIN sms
       ON grouped.smsCONID     = sms.smsCONID
      AND grouped.smsTIMESTAMP = sms.smsTIMESTAMP
ORDER BY smsTIMESTAMP DESC