Android 使用别名的 Sqlite 多重连接没有 return 任何东西

Question

我有这个查询：

 Cursor res = db.rawQuery("SELECT t1.Id, t2.EmpId FROM table1 t1 
                              LEFT JOIN table2 t2 ON t1.t2Id = t2.Id
                              LEFT JOIN table3 t3 ON t1.t3Id = t3.Id
                           WHERE t1.Id = 90909", null);

现在我去的时候

if(res.moveToFirst()){
   do{
        MyObject obj = new MyObject();
        obj.Id = res.getInt(res.getColumnIndex("t1.Id"));

        MyObjectAsProperty objProp = new MyObjectAsProperty();
        objProp.EmpId = res.getInt(res.getColumnIndex("t2.EmpId"));
   }while(res.moveToNext());
}

objProp.EmpId returns 什么都没有（或0）。我查看了游标列，它的字段基本上不包含 table 别名。我该如何获取这些别名字段的值？

谢谢！

编辑

抱歉。我忘了补充一点，例如，如果它在同一字段中多次引用相同的其他 table。

这是更新后的查询

Cursor res = db.rawQuery("SELECT t1.Id, t2.EmpId, t2b.EmpId FROM table1 t1 
                                  LEFT JOIN table2 t2 ON t1.t2Id = t2.Id
                                  LEFT JOIN table2 t2b ON t1.t2bId = t2b.Id
                               WHERE t1.Id = 90909", null);

if(res.moveToFirst()){
       do{
            MyObject obj = new MyObject();
            obj.Id = res.getInt(res.getColumnIndex("t1.Id"));

            MyObjectAsProperty objProp = new MyObjectAsProperty();
            objProp.EmpId = res.getInt(res.getColumnIndex("t2.EmpId"));

            MyObjectAsProperty objProp2 = new MyObjectAsProperty();
            objProp2 .EmpId = res.getInt(res.getColumnIndex("t2bId.EmpId"));
       }while(res.moveToNext());
    }

Answer 1

documentation 说：

The name of a result column is the value of the "AS" clause for that column, if there is an AS clause. If there is no AS clause then the name of the column is unspecified and may change from one release of SQLite to the next.

所以你必须使用 AS:

SELECT t1.Id AS ObjID, t2.EmpId AS EmpId, ...

Android 使用别名的 Sqlite 多重连接没有 return 任何东西

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