Parse.com相当于SQL连接 [英] Parse.com equivalent to SQL joins
问题描述
我知道Parse.com是一个NoSQL数据库和SQL概念不应该被应用到它，反正，除了理论，我敢打赌，有一种方式解析的东西做这样的经典SQL连接
例如，假设我们在我们的数据库3个表/班：人民，城市和国家，与示例值在括号
人物：
-name（马里奥·罗西）
- 年龄（23）
- 城市（博洛尼亚）城市：
-name（博洛尼亚）
-Postal code（40100）
-country（意大利）国家：
-name（意大利）
-Continent（欧洲）
由于这种结构，比方说，我想知道在哪个洲的人马里奥·罗西，23岁，家住。在传统的SQL方法这就好像很容易实现：
距离人民选择People.Name，People.Age，Countries.Continent
JOIN中的城市People.City = Cities.name
JOIN上City.Country = Countries.Name国家
凡People.Name ='马里奥·罗西
结果记录将是马里奥·罗西，23，欧洲。现在，如果我想和解析，或者更好，如果我想获得的相同的结果与解析，怎么我的结构看起来一样的东西？我应该使用指针？参考文献？我读到这些结构的，但我不知道他们是否适用于这种情况下，以及如何使用它们。
我正在开发在Android中，但由于这是一个基本的问题，我想我可以接受/基于其他平台也明白的答案。
感谢您！
Fosco建议后编辑：
公共类CustomAdapter扩展ParseQueryAdapter＆LT;＆的parseObject GT;实现OnItemClickListener {
公共CustomAdapter（上下文的背景下）{
超（背景下，新ParseQueryAdapter.QueryFactory＆LT;＆的parseObject GT;（）{
公共ParseQuery＆LT;＆的parseObject GT;创建（） {
ParseQuery＆LT;＆的parseObject GT;查询= ParseQuery.getQuery（人物）;
query.include（城市）;
query.include（City.Country）;
query.whereEqualTo（姓名，马里奥罗西）;
返回查询;
}
}）;
} @覆盖
公共查看getItemView（的parseObject的parseObject，视图V的ViewGroup以及母公司）{
如果（V == NULL）{
V = View.inflate（的getContext（），R.layout.row_ppl为null）;
} super.getItemView（的parseObject，V，父母）;
城市的parseObject = parseobject.getParseObject（城市）;
国家的parseObject = City.getParseObject（国家）;
字符串大陆= country.getString（大陆）; TextView的诺姆=（TextView中）v.findViewById（R.id.textView1）;
nome.setText（parseobject.getString（姓名））;
TextView的CONT =（TextView中）v.findViewById（R.id.textView2）;
cont.setText（大陆）; 返回伏; } @覆盖
公共无效onItemClick（适配器视图＆LT;＆GT;为arg0，ARG1观，诠释ARG2，长ARG3）{
Log.d（rilevato，点击）; }}
如果您创建国家和城市作为解析类，并且使用指针，你可以做到这一点很容易。
城市包含一个指向国家，列名国家
人们包含一个指向城市，列名城市
VAR的查询=新Parse.Query（人物）;
query.include（城市）;
query.include（'city.country'）;
query.equalTo（'名'，'马里奥罗西'）;
query.first（），然后（功能（的人）{
的console.log（人）;
}，功能（错误）{}）;
您将有完整的城市和放大器;当你拉国家记录的人的记录。
编辑添加的Android例如：
ParseQuery＆LT;＆的parseObject GT;查询= ParseQuery.getQuery（人物）;
query.include（城市）;
query.include（city.country）;
query.whereEqualTo（姓名，马里奥罗西）;
query.getFirstInBackground（新GetCallback＆LT;＆的parseObject GT;（）{
公共无效做过（的parseObject人，ParseException的E）{
如果（E == NULL）{
城市的parseObject = object.get（城市）;
国家的parseObject = city.get（国家）;
字符串大陆= country.get（大陆）;
}其他{
Log.d（人，错误：+ e.getMessage（））;
}
}
}）;
I know that Parse.com is a NoSql database and SQL concepts should not be applied to it, anyway, besides theory, i bet there is a way to do in Parse something like classic SQL joins.
For example, assume we have 3 tables/classes in our DB: People, Cities and Countries, with example values in brackets.
People:
-Name (Mario Rossi)
-Age (23)
-City (Bologna)
Cities:
-Name (Bologna)
-PostalCode (40100)
-Country (Italy)
Countries:
-Name (Italy)
-Continent (Europe)
Given this structure, let's say I want to know in which continent the person Mario Rossi, aged 23, lives. In a classical SQL approach this would be accomplished easily like:
select People.Name,People.Age,Countries.Continent from People
JOIN Cities on People.City = Cities.name
JOIN Countries on City.Country = Countries.Name
Where People.Name = 'Mario Rossi'
The resulting recordset would be "Mario Rossi, 23, Europe". Now, if i want to make the same thing with Parse, or better, if i want to get the same result with Parse, what should my structure look like? Should i use pointers? References? I read about these structures but i don't know if they apply to this case and how to use them. I'm developing in Android, but since this is a basic question i think i may accept/understand answers based on other platforms too.
Thank you!
Edit after Fosco suggestions:
public class CustomAdapter extends ParseQueryAdapter <ParseObject> implements OnItemClickListener{
public CustomAdapter(Context context) {
super(context, new ParseQueryAdapter.QueryFactory<ParseObject>() {
public ParseQuery<ParseObject> create() {
ParseQuery<ParseObject> query = ParseQuery.getQuery("People");
query.include("City");
query.include("City.Country");
query.whereEqualTo("Name","Mario Rossi");
return query;
}
});
}
@Override
public View getItemView(ParseObject parseobject, View v, ViewGroup parent) {
if (v==null){
v = View.inflate(getContext(), R.layout.row_ppl, null);
}
super.getItemView(parseobject, v, parent);
ParseObject city = parseobject.getParseObject("City");
ParseObject country = City.getParseObject("Country");
String continent = country.getString("Continent");
TextView nome = (TextView) v.findViewById(R.id.textView1);
nome.setText(parseobject.getString("Name"));
TextView cont = (TextView) v.findViewById(R.id.textView2);
cont.setText(continent);
return v;
}
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
Log.d("rilevato ", "click");
}
}
If you create Country and City as classes on Parse, and use pointers, you can do this very easily.
Cities contains a pointer to Countries, column name 'country'
People contains a pointer to Cities, column name 'city'
var query = new Parse.Query("People");
query.include('city');
query.include('city.country');
query.equalTo('Name', 'Mario Rossi');
query.first().then(function(person) {
console.log(person);
}, function(err) {
});
You'll have the full city & country records when you pull the people record.
edit to add Android example:
ParseQuery<ParseObject> query = ParseQuery.getQuery("People");
query.include("city");
query.include("city.country");
query.whereEqualTo("Name", "Mario Rossi");
query.getFirstInBackground(new GetCallback<ParseObject>() {
public void done(ParseObject person, ParseException e) {
if (e == null) {
ParseObject city = object.get("city");
ParseObject country = city.get("country");
String continent = country.get("continent");
} else {
Log.d("person", "Error: " + e.getMessage());
}
}
});
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