SSRS: Grouping

In our last lesson we made the basic report seen below:


**Note, you can follow the link below to the first lesson:

SSRS: Introdution: 1rst Report


Our data is currently in table form, but is otherwise still nothing more than a raw data dump. Let’s make our report a little nicer with some grouping. Right click on the data row (not header) in your table. Mouse over to Add Group and select Parent Group…


In the new window, select [Name] from the drop down.


Click Add group header and Add group footer boxes. Now click OK


Now a group has been added to your report.


If you click on preview, you will now see the table is grouped by Names


But you will notice we now have 2 columns showing the Name, one – our new grouping column and the other – the original column. This is redundant. To get rid of it, go back to Design, right click on the second name column and select Column Visibility…


When the new window opens up, click Hide.


Now when you look at the report now, you will see the second Name column is now hidden.


Running Total:

Next, let’s set up a running total for Hours spent on each job. To do so, right click on the Hours text box and select Add Total


Now when we go back to preview, we will see at total in the group footer for each person



Now what if we wanted an average instead? Right click on the textbox that says [Sum(Hours)] and select Expression


You can just type = Avg(Fields!Hours.Value) in the expression builder box, but if you don’t know the code, you can use information in the boxes below. As you can see in the example below, if you go to Common Functions > Aggregate you will see the code for lots of functions like Average, count, standard deviation.


Now when you go to preview, you will see an average.

But now we have a new problem. If you are trying to average something like work hours, odds are you will not need to go out to 10 decimal places. So a number like 8.272727272727 is pretty much ridiculous for a report like this.


Now go to Number > Number and set the Decimal Places to 2


So if you look at it again, you will see you only have 2 decimal points now.





Blockchain: P2p distributed networks

Another concept you need to be familiar with to understand Blockchain is the concept of a P2p distributed network. This is the physical architecture that allows Blockchain to work and provides a blockchain with redundancy.

The P2P in P2P distributed network stands for peer to peer, indicating a network comprised of peers. What do I mean by that? The majority of computer networks in place right now are what is known as Server/Client networks.

In the picture below, the center square represents a server, with the boxes around it representing nodes (or in your case, the computer/tablet/phone you are reading this on). When you want to view a web page, you send a request from your node to a server. The server will then respond with the requested information.


While this works well, it does have some drawbacks.   First off, since the server is central point of communication and the holder of all the information (webpages, databases, etc), if the server goes down, the network is essentially dead. This is the whole idea behind one of the more successful methods of cyber attack – the Denial of Service in which a server is targeted with more traffic than it can handle, shutting it down. You will often see it called a Distributed Denial of Server of DDoS as in order to hit the server with enough traffic to break it, hackers use multiple computers synced to deliver enough requests to the server all at the same time, overwhelming it. In other words, the attack is “distributed” across multiple computers.


Blockchain does not use a server client approach. Instead it uses a P2p or peer to peer network to function.  In a peer to peer, the nodes (laptops, tablets, etc) all talk directly to each other. Instead of a server holding all the information, the data that makes up the blockchain is instead distributed across all the different nodes. So the more nodes that are part of the blockchain, the more copies of it that exist.


This works great for redundancy as even if you took out a couple of nodes in the network, it would still be able to function as normal. And as we will see a future lesson, even if you were able to hack in and corrupt the blockchain in one of the nodes, the fact that copies of it exist on all the other nodes protect it from corruption.

This architecture is also at the heart of philosophy around crypto-currencies like BitCoin. Unlike traditional banking systems that have centralized management, BitCoin is programmed with a deflationary policy that no one person (or group of person) can control. This is an interesting economic experiment unfurling before all of us. And I for one am curious to see how it plays out. While organizations like the Fed (in the United States) have done a relatively good job of keeping the US dollar strong, poor centralized economic management has spelled disaster in countries like Venezuela and Zimbabwe.

I’ll discuss more on the economic theory behind BitCoin in later lessons. It is enough for now for you to know that the P2P decentralized nature of the network is all part of the design in ensuring no one person can make such drastic changes.

If you want to learn more about networks and how they interact, here are some further resources:,3020.html

Blockchain: Immutable Ledger

The next concept we need to cover to properly understand blockchain is the concept of an Immutable Ledger.  To translate this term into something that looks more like English, an Immutable Ledger simply means a record that cannot be changed.

The idea behind all of this is data security and proof that the data has not been altered. Why are we so concerned here? In a blockchain application like BitCoin, we are tracking transactions of money. Imagine if you sent me an electronic funds transfer for $100. How would you feel if I hacked into your bank and changed that $100, to $100,000? (For the record, if you tried that with my account, the computer would just laugh at you. The only time you’ll see a number that big associated with me is when you are looking at my student loans LOL).

Anyway, back to the point, you want to make sure that when you set up a transfer for $100, no one can alter it. With blockchain, that is true even if you want it to be altered (you made a mistake). If you want to fix an error, you will have to add another transaction to the blockchain to correct the issue. This is actually good accounting practice, as once an entry is made into a ledger, it should never be removed or altered.

Think of this like purchasing a car. If you go to your neighbor and buy his used car for $2000. You give him the money, and he signs over a title to you. The title is proof of ownership. To ensure that your neighbor cannot just take the car back, you take the title down to the Department of Motor Vehicles and have the title registered in your name. Now you have a record of your transaction should the ownership of the vehicle ever come into question.

So how does blockchain ensure immutability of the ledger? It all resides in the concept of the hash. If hacker tries to alter anything in the block below, its hash will change. Now the hash will no long match the previous hash in the second block. So, the hacker would have to change the next block, and the block after that, etc.


And even if they were able to pull that off, remember that the blockchain resides on multiple computers. The hacker would need to make all of these changes simultaneously. When you consider the millions of nodes that make up a blockchain environment like BitCoin, you will see that would be impossible.


In the next lesson, we will be looking at peer to peer distributed networks

Blockchain: Cryptographic Hash

To fully understand blockchain, it helps to have a good understanding of what is known as a cryptographic hash. It is this hash that is at the very core of how blockchain works.

If you read my introduction to blockchain lesson, you would see that the Hash is part of every block. It serves as a unique identifier for the block. That is the general idea for all Hashes, whether cryptographic or not.


It would actually be more proper for me to refer to it as a Hash Function. It is a function where you pass in text, a document, a picture, anything digital, and the function will return a unique identifying number.

Hash functions were used even before cryptography was an issue. You may have heard the term Hash Tables, this is where computer programmers would store a table full of hashes indicating text or documents, instead of having to store large documents in memory.

The Hash tables worked kind of like this:

You would pass some text to the Hash Function and it would transform it to a hash.

Ben -> 0123
Data Science -> 4871
Analytics is a great field of study -> 2580

These hashes were then placed in a table and when the program needed to access the information, it used the Hash to look it up – kind of like an index in the back of a book.

Now the Hash Functions used by Blockchain are cryptographic, so they are a little different than just a simple hash table. In order for a hash to be cryptographic, it needs to follow some basic rules.

  1. It has to be 1 way. If you pass the text “Analytics” to a cryptographic hashing function it will return a hash(let’s say 1234). It will return the same hash every time you pass the text “Analytics” to it (again: 1234). So the hash function knows what hash to create for that text. But, we want to ensure that if someone has the hash 1234, they cannot reverse it to obtain the text (they can’t reverse engineer it)

Think of it like a finger print. If I have person, I can always obtain a fingerprint.                  However, if all I have is a fingerprint, I cannot produce a person from it. A finger               print on its own won’t let me derive information like eye color or hair color of the             individual who left print behind.

  1. The hash function needs to be fast. You will understand better when we get to mining, but blockchain miners are passing millions of a hashes a second. With a slow hash function, the entire concept would fail.
  2. The hash needs to ensure that similar items do not receive similar hashes. The example below shows what we do not want.
Text Hash
Analytics 1234
Analytics4 1235


With the hashes 1234 and 1235 being so close as well as the text being so close, it would make it possible to reverse engineer a hash. For example, if you knew that Analytics4all was 1236, you might be able to back track the hash until you hit analytics at 1234

Instead we want something like this:

Text Hash
Analytics 1234
Analytics4 8476


You see the similar text do not get similar hashes. Let’s look at it through numbers

Number Hash
20 8463
21 1258
22 6581
23 0874


Now different blockchain applications will use different cryptographic hash functions, For example, Etherium uses MD-5. BitCoin, however uses SHA-256, so that is what I will focus on.

SHA-256 was created by the NSA and as of this writing, it has not been cracked. The code for SHA-256 is open source, so anyone can  make use of it.

A SHA-256 HASH is 64 hexidecimal digits long  (64 digits * 4 bits per digit = 256).

Here is a SHA-256 HASH


If you want to try it out, go to this website

Below, I pass the text Analytics to the hash generator and I get a 64 digit hash returned


Now when I just add the number 4 to the end of my text, the hash completely changes. The two hashes do not look anything alike. Again, this is designed to help reduce the chance of someone reverse engineering the hash.


Just to drive the point home. Here is removed the s from the end of the text. Note the new hash is again completely different.


Go to the website. Try out some hashing for yourself.

In the next lesson I will cover the concept of an imputable ledger. This will take us one step closer to understanding Blockchain.

Blockchain: An Introduction

Unless you’ve been living under a rock, you have undoubtedly heard the  term blockchain being batted around. Most likely you’ve heard of it in relation to cryptocurrency like BitCoin, but blockchain is quickly moving into many other areas. Much like the Big Data craze though, my personal experience has been the more you hear someone utter the term blockchain, the less that person actually knows about it. It is the Dunning-Kruger Effect in action.

In this lesson, I am going to introduce you to the concept of blockchain. I have boiled it down to its simplest concepts, and I will be speaking very broadly about the subject. In future lessons I will dive deeper into the more technical aspects of blockchain, providing much more in the way of specifics.

For those already familiar with blockchain, I am aware that I am glossing over some rather important concepts here, but my goal in this lesson is to provide a simple, easily understood tutorial. The goal of my website is to provide an accessible education into many of the complex concepts surrounding analytics and data science to everyone, regardless of past experience or education. I promise a deeper dive in the future, but for now, let us start simply.

What is a blockchain?

At the most basic level, a blockchain is a collection of data kept in a list.


What makes these lists so interesting is that:

  1. They are connected using cryptography
  2. They are distributed amongst multiple computers, providing a redundant method of protection

To understand how they work, let us start by looking at a block


Starting from the top

Block #: is just the number of the block in the chain, first block # is 1, second is 2, so on

Nonce: stands for “number used only once”. I am going to cover the Nonce in depth in the lesson on Mining, but for right now, just be aware that it is a number and every block needs a Nonce

Data: This is where the data is stored. In BitCoin this is often filled with transaction information

Previous Hash: The hash of the block before this one

Hash: I will cover hashes in depth in a future lesson two. For now, just know this the cryptographic part of blockchain. A hash is a code number that identifies the block. An easy way to conceptualize it is to think of it like a VIN on a car. The VIN (or vehicle identification number) can be used to tell you the make, model, color, and many other characteristics of a car. The hash (in blockchain) will tell you everything found in the block (I know I am way over simplifying here, but hey we have to start somewhere, and I promise a future lesson on hash)

Now let’s add a second block to our chain

Notice the previous hash in block 2 is the same as the hash in block 1. This, you will soon see, is part of what makes blockchain so secure.


In the picture below, you can see if someone tried to go into Block 1 and make a change, the Hash for block 1 would change. Any change to the first four fields in a block will cause the Hash to chance since the block is no longer the same anymore. The Hash is like a VIN or a fingerprint, it can only represent a single individual block. And once you change any aspect of a block, it is no longer the same individual block anymore.


So as you can see, if the Hash in the first block changes, it will no longer match the Previous Hash in the second block. When this happens the blockchain is broken. So if a hacker tried to alter a transaction in block 1, the chain would break.

Okay, so what is to prevent the hacker from just changing the second block? Aside from hashing issues that we will discuss in future lessons? The other deterrent is found in peer to peer sharing of blockchains

In most real world applications of blockchain, the chain will not reside on only one computer, instead will be replicated across multiple computers.


So now if a hacker tries to change the third block on one computer.


The third blocks hash will change, breaking its connection from the fourth block


And even more importantly, the chain will no longer look like the one on the second computer. Now in real life, this will be spread across thousands of computers. So to determine which blockchain is correct, they look to see what iteration the majority of computers say is correct.

So as seen below, 3 of the 4 computers show 4 blue squares, while only one was a yellow square. So based on the vote of the majority, the final result will be 4 blue squares.


So there you have it, blockchain in its most simplistic form. In future lessons I’ll dive deeper in the different concepts to show how it works from the inside out.





Click below for an interesting link for BitCoin information

Alexus Security