Try having a look at [Database Answers][1] in particular the data models. They have several different designs for various systems. This [one][2] is for a social networking site which may give you an idea of what&#39;s required. 

You may want to search on SO for other social network database questions. I found [this one][3] that had a link to [flickr][4] showing a schema which appears to be from Facebook. 

Your database design will be based around your system requirements. Without knowing exactly what you are trying to achieve, it is difficult to give you the best design. 

  [1]: http://www.databaseanswers.org/data_models/index.htm
  [2]: http://www.databaseanswers.org/data_models/social_networking/index.htm
  [3]: https://stackoverflow.com/questions/2767034/social-networking-network-affiliations
  [4]: http://www.flickr.com/photos/ikhnaton2/533233247/

You can create a separate table for follower/ followed `relationships`. So, when x follow y, create an entry with `follower_id = x.id followed_id = y.id`. 

You can query the relationship table to look for all the users x has relations with by `select * from relationships where follower_id = x.id` or vice versa. 

When/if x un-follow y, you just have to delete the entry you originally created.      

you can use this Messenger Database Design Concept: [Messenger DB][1]

[![Messenger DB Schema][2]][2]


  [1]: https://github.com/yoosuf/Messenger
  [2]: https://i.stack.imgur.com/UfoS9.png

I have an issue with the following error in Android:

&gt; CalledFromWrongThreadException;: Only
&gt; the original thread that created a
&gt; view hierarchy can touch its views

It appears to happen when I try to update a Textview in my Activity, the call to update the TextView is from within my Activity but I still get the above error.

I have it like this:

onCreate()
-sets up the buttons and the text view.

onStateChange() - a listener for notifications about state changes, when this gets notification if changes the TextView to say some different text.

When I get notification of a new text I try to change the TextView as so:

    ((TextView)findViewById(R.id.title)).setText(&quot;Some Text&quot;);

But I get the above Error.

From googling it, it appears I should use a handler to change the TextView or maybe use AsyncTask?

Could anyone explain which one would be better to use and why?

**EDIT: ADDED CODE SNIPPETS:**

---

		 public void onCreate(Bundle savedInstanceState) {
		        super.onCreate(savedInstanceState);
		        
				requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);	

				setContentView(R.layout.my);
		        
				getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.my_title);	

				((TextView)findViewById(R.id.time)).setText(&quot;Hello Text&quot;);

				
				findViewById(R.id.keyboardimage).setOnClickListener(new OnClickListener() {
		            public void onClick(View v) {
		            	
		            	Intent dialIntent = new Intent(Intent.ACTION_DIAL, Uri.parse(&quot;tel:&quot;));
		        		startActivity(dialIntent);
		        		
		                    dispatchKeyEvent(new KeyEvent(KeyEvent.ACTION_DOWN,KeyEvent.FLAG_SOFT_KEYBOARD));
		                    dispatchKeyEvent(new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_BACK));       
		            }
		    });
				
		 }


---

    //CallBacks from running Service

    private final ICallDialogActivity.Stub iCallDialogActivity = new ICallDialogActivity.Stub(){

    @Override
    public void onStateChanged(int callState)
					throws RemoteException {	
				switch(callState){
				case GlobalData.CALL_STATUS_IDLE:
					 
					break;
					
				case GlobalData.CALL_STATUS_DISCONNECTING:
					byeSetup();
					break;
        } 

    };

---

    public void byeSetup(){
		    	
		    	((TextView)findViewById(R.id.time)).setText(&quot;Bye Text&quot;);
		    	
		    	findViewById(R.id.keyboardimage).setOnClickListener(new OnClickListener() {
		            public void onClick(View v) {
		            	//Void the Button
		            }});
    }


CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch views

If I have an apk can I remove the current signing and some how re-sign it with a different .keystore file and still have the application install?


**Update**: I managed to get it to work with Jorgesys&#39; solution and where I messed up before was that I unzipped the .apk then rezipped it after removing the META-INF folder and changed the file extension back into .apk. What I should have done is simply opened it with winzip and delete the folder inside of winzip.

Can I re-sign an .apk with a different certificate than what it came with?

What are the Tables that would be present in a social networking site (ex: Twitter).

I have a users table as of now. How to keep track of followers and people I do follow?

 - Should I maintain a separate table for followers and people I follow?
 - What are the columns which would be there in those tables?

Please don&#39;t think this as Subjective/Off topic. As I am a beginner, I thought experts can guide me to get a good DB design?

Database design for a social networking site

What are the Tables that would be present in a social networking site (ex: Twitter).
I have a users table as of now. How to keep track of followers and people I do follow?
<ul>
<li>Should I maintain a separate table for followers and people I follow?</li>
<li>What are the columns which would be there in those tables?</li>
</ul>
Please don't think this as Subjective/Off topic. As I am a beginner, I thought experts can guide me to get a good DB design?

How do I combine two columns and apply filter? For example, I want to search in both the &quot;firstname&quot; and &quot;lastname&quot; columns at the same time.  Here is how I have been doing it if searching only one column:

    query = meta.Session.query(User).filter(User.firstname.like(searchVar))



 

sqlalchemy filter multiple columns

The **BASE** acronym is used to describe the properties of certain databases, usually NoSQL databases. It&#39;s often referred to as the opposite of [ACID](http://en.wikipedia.org/wiki/ACID).

There are only few articles that touch upon the details of BASE, whereas ACID has plenty of articles that elaborate on each of the atomicity, consistency, isolation and durability properties. Wikipedia only devotes [a few lines](http://en.wikipedia.org/wiki/Eventual_consistency) to the term.

This leaves me with some questions about **the definition**:

&gt; &lt;b&gt;B&lt;/b&gt;asically &lt;b&gt;A&lt;/b&gt;vailable, &lt;b&gt;S&lt;/b&gt;oft state, &lt;b&gt;E&lt;/b&gt;ventual consistency

I have interpreted these properties as follows, using [this article](http://queue.acm.org/detail.cfm?id=1394128) and my imagination:

**Basically available** could refer to the perceived availability of the data. If a single node fails, part of the data won&#39;t be available, but the entire data layer stays operational.

* Is this interpretation correct, or does it refer to something else?
* **Update:** deducing from [Mau&#39;s answer](https://stackoverflow.com/questions/3342497/explanation-of-base-terminology/3342749#3342749), could it mean the entire data layer is always accepting new data, i.e. there are no locking scenarios that prevent data from being inserted immediately?

**Soft state**: All I could find was the concept of data needing a period refresh. Without a refresh, the data will expire or be deleted.

* Automatic deletion of data in a database seems strange to me.
* Expired or stale data makes more sense. But this concept would apply to any type of redundant data storage, not just NoSQL. Does it describe something else then?

**Eventual consistency** means that updates will eventually ripple through to all servers, given enough time.

* This property is clear to me.

---

Can someone explain these properties in detail?

Or is it just a far-fetched and meaningless acronym that refers to the concepts of acids and bases as found in chemistry?

Explanation of BASE terminology

Which query will give the table structure with column definitions in SQL?

Describe table structure

What I need is a migration to apply unique constraint to a combination of columns. i.e. for a `people` table, a combination of `first_name`, `last_Name` and `Dob` should be unique.

A migration to add unique constraint to a combination of columns

I have created a database for my android app which contains static data and does not require update/delete functionality thus when the app starts, I want to check if the db exists and if not then execute my dbAdapter class. I know its a simple if statement but I was just wondering the most efficient way to query whether the db exists. 

Cheers 

Query if Android database exists!

Is there a tool or method to analyze Postgres, and determine what missing indexes should be created, and which unused indexes should be removed? I have a little experience doing this with the &quot;profiler&quot; tool for SQLServer, but I&#39;m not aware of a similar tool included with Postgres.

PostgreSQL Index Usage Analysis

I&#39;m thinking about how to represent a complex structure in a SQL Server database.

Consider an application that needs to store details of a family of objects, which share some attributes, but have many others not common. For example, a commercial insurance package may include liability, motor, property and indemnity cover within the same policy record.

It is trivial to implement this in C#, etc, as you can create a Policy with a collection of Sections, where Section is inherited as required for the various types of cover. However, relational databases don&#39;t seem to allow this easily.

I can see that there are two main choices:

 1. Create a Policy table, then a Sections table, with all the fields required, for all possible variations, most of which would be null.  
 
 3. Create a Policy table and numerous Section tables, one for each kind of cover.

Both of these alternatives seem unsatisfactory, especially as it is necessary to write queries across all Sections, which would involve numerous joins, or numerous null-checks.

What is the best practice for this scenario?

How can you represent inheritance in a database?

Imagine a web form with a set of check boxes (any or all of them can be selected). I chose to save them in a comma separated list of values stored in one column of the database table.

Now, I know that the correct solution would be to create a second table and properly normalize the database. It was quicker to implement the easy solution, and I wanted to have a proof-of-concept of that application quickly and without having to spend too much time on it.

I thought the saved time and simpler code was worth it in my situation, is this a defensible design choice, or should I have normalized it from the start?

Some more context, this is a small internal application that essentially replaces an Excel file that was stored on a shared folder. I&#39;m also asking because I&#39;m thinking about cleaning up the program and make it more maintainable. There are some things in there I&#39;m not entirely happy with, one of them is the topic of this question.

Is storing a delimited list in a database column really that bad?

Is email address a bad candidate for primary when compared to auto incrementing numbers?

Our web  application needs the email address to be unique in the system. So, I thought of using email address as primary key. However my colleague suggests that string comparison will be slower than integer comparison. 

Is it a valid reason to not use email as primary key?

We are using `PostgreSQL`.

Use email address as primary key?

Some co-workers and I got into a debate on the best way to store historical data.  Currently, for some systems, I use a separate table to store historical data, and I keep an original table for the current, active record.  So, let&#39;s say I have table FOO.  Under my system, all active records will go in FOO, and all historical records will go in FOO_Hist.  Many different fields in FOO can be updated by the user, so I want to keep an accurate account of everything updated.  FOO_Hist holds the exact same fields as FOO with the exception of an auto-incrementing HIST_ID.  Every time FOO is updated, I perform an insert statement into FOO_Hist similar to: `insert into FOO_HIST select * from FOO where id = @id`.  

My co-worker says that this is bad design because I shouldn&#39;t have an exact copy of a table for historical reasons and should just insert another record into the active table with a flag indicating that it&#39;s for historical purposes.

Is there a standard for dealing with historical data storage?  It seems to me that I don&#39;t want to clutter my active records with all of my historical records in the same table considering that it may be well over a million records (I&#39;m thinking long term).

How do you or your company handle this?

I&#39;m using MS SQL Server 2008, but I&#39;d like to keep the answer generic and arbitrary of any DBMS.

How to Store Historical Data

Integrating Multiple Social networks into Android with a single common Framework or API or JAR


 **For iPhone we have ShareKit, which integrates multiple sharing options in one framework.
http://www.getsharekit.com/**

For android i have no idea if something similar exists. I am building an application which shares information to social networks, like some posts and tweets. Its a simple game, where gamers publish updates about their achievements and levels.. etc.. I used Facebook and twitter APIs but they take up lots of memory and difficult to manage. Also i cannot handle them efficiently. Any help on how to integrate them would be appreciated.

I would like to have a few suggestions on this.. 

Another Example seems PinkelStar

&lt;strike&gt;http://www.pinkelstar.com/&lt;/strike&gt;
(Not maintained anymore)

Thanks

Integrating FaceBook, Twitter, Social networks in Android

We used the link: 

    http://www.facebook.com/sharer.php?u=[shared URL]

...to share a particular page. However, Facebook Sharer uses the cached version of the images and the title. Is there a way to quickly clear the Facebook cache or how long do we have to wait until the data gets updated?

I placed `&lt;link rel=&#39;image_src&#39; href=&#39;[preview image]&#39; /&gt;` in between the &lt;head&gt;&lt;/head&gt; tags.




How to clear Facebook Sharer cache?

I&#39;m interested in network analysis on large networks with millions of nodes and tens of millions of edges.  I want to be able to do things like parse networks from many formats, find connected components, detect communities, and run centrality measures like PageRank.

I am attracted to NetworkX because it has a nice api, good documentation, and has been under active development for years.  Plus because it is in python, it should be quick to develop with.

In a recent presentation (the slides are available on github [here][1]), it was claimed that:

&gt; Unlike many other tools, NX is designed to handle data on a scale
relevant to modern problems...Most of the core algorithms in NX rely on extremely fast legacy code.

The presentation also states that the base algorithms of NetworkX are implemented in C/Fortran.

However, looking at the source code, it looks like NetworkX is mostly written in python.  I am not too familiar with the source code, but I am aware of a couple of examples where NetworkX uses numpy to do heavy lifting (which in turn uses C/Fortran to do linear algebra).  For example, the file `networkx/networkx/algorithms/centrality/eigenvector.py` uses numpy to calculate eigenvectors.

Does anyone know if this strategy of calling an optimized library like numpy is really prevalent throughout NetworkX, or if just a few algorithms do it?  Also can anyone describe other scalability issues associated with NetworkX?

**Reply from NetworkX Lead Programmer**
I posed this question on the NetworkX mailing list, and Aric Hagberg replied:

&gt; The data structures used in NetworkX are appropriate for scaling to
&gt; large problems (e.g. the data structure is an adjacency list).  The
&gt; algorithms have various scaling properties but some of the ones you
&gt; mention are usable  (e.g. PageRank,  connected components, are linear
&gt; complexity in the number of edges).
&gt; 
&gt; At this point NetworkX is pure Python code.  The adjacency structure
&gt; is encoded with Python dictionaries which provides great flexibility
&gt; at the expense of memory and computational speed.  Large graphs will
&gt; take a lot of memory and you will eventually run out.
&gt; 
&gt; NetworkX does use NumPy and SciPy for algorithms that are primarily
&gt; based on linear algebra.  In that case the graph is represented
&gt; (copied) as an adjacency matrix using either NumPy matrices or SciPy
&gt; sparse matrices.  Those algorithms can benefit from the legacy C and
&gt; FORTRAN code that is used under the hood in NumPy and SciPY.

  [1]: https://github.com/drewconway/NetworkX_Intro_Materials

What scalability issues are associated with NetworkX?

Since I found some older posts, that tell that whatsapp doesn&#39;t support this, I was wondering if something had changed and if there is a way to open a whatsapp &#39;chat&#39; with a number that I&#39;m sending through an intent?

Sending message through WhatsApp

I have seen this format (Image shown below) of share option in most of the iOS applications that support iOS 7.
Is there a default code/framework available to implement this share option as it is shown in the image below?

![][1]


  [1]: http://i.stack.imgur.com/BxgKk.png

Content Type	Original Author	Original Content on Stackoverflow
Question	user326638	View Question on Stackoverflow
Solution 1 - Database	Andy Robinson	View Answer on Stackoverflow
Solution 2 - Database	user3375663	View Answer on Stackoverflow
Solution 3 - Database	Sadegh-khan	View Answer on Stackoverflow

Database design for a social networking site

Database Problem Overview

Database Solutions

Solution 1 - Database

Solution 2 - Database

Solution 3 - Database

Can I re-sign an .apk with a different certificate than what it came with?

CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch views

Attributions