Question

此函数始终返回false并且游标始终为空，即使数据库中有10条记录，我尝试使用分配ID查询每条记录但不起作用。

我已将数据库从虚拟设备复制到我的电脑中，并使用sqlite manger进行相同的查询，并在PC中工作，数据库中有所有记录。

这是我的代码：

public boolean checkAssignment(String assignmentId) {
        boolean assignmentStored = false;
        String selectQuery = "SELECT * FROM " + TABLE_ASSIGNMENTS +
                " WHERE " + KEY_ASSIGNMENT_ID + " = '" + assignmentId.trim()+"'";
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        if (cursor.getCount() > 0) {
            assignmentStored = true;
        }
        cursor.close();
        return assignmentStored;
}

Answer 1

根据您发布的图片，我可以看到assignmentId列的数据类型为数字。

因此请更改您的查询：

String selectQuery = "SELECT * FROM " + TABLE_ASSIGNMENTS +
     " WHERE " + KEY_ASSIGNMENT_ID + " = " + Integer.parseInt(assignmentId.trim());

Answer 2

以这种方式使用：

public boolean checkAssignment(String assignmentId) {
        boolean assignmentStored = false;    
        String[] columnsToReturn = { "KEY_ASSIGNMENT_ID"};
        String selection = "KEY_ASSIGNMENT_ID =?";
        String[] selectionArgs = { Integer.ParseInt(assignmentId.trim())}; 

        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor =  db.query(TABLE_ASSIGNMENTS, columnsToReturn, selection, selectionArgs, null, null, null);

        if (cursor.getCount() > 0) {
            assignmentStored = true;
        }
        cursor.close();
        return assignmentStored;
    }

SQLlite：选择where子句不起作用的查询

2 个答案: