If the database that you work with supports Window/Analytic functions then the chances are that you have run into SQL use-cases where you have wondered about the difference between Row_Number(), Rank() and Dense_Rank(). In this post, I’ll show you the difference:
So, let’s just run all of them together and see what the output looks like.
Row_Number() OVER (Order by Reputation desc) as RowNumber,
Rank() OVER (Order by Reputation desc) as Rank,
Dense_Rank() OVER (Order by Reputation desc) as DenseRank
Note that all the functions are essentially are “ranking” your rows but there are subtle differences:
Row_Number() doesn’t care if the two values are same and it just ranks them differently. Note row #2 and #3, they both have value 9997 but they were assigned 2 and 3 respectively.
Rank() — Now unlike Row_Number(), Rank() would consider that the two values are same and “Rank” them with same value. Note Row #2 and #3, they both have value 9997 and so both were assigned Rank “2” — BUT notice the Rank “3” is missing! In other words, it introduces some “gaps”
Dense_Rank() — Now Dense_Rank() is like Rank() but it doesn’t leave any gaps! Notice that the Rank “3” in the DenseRank field.
I hope this clarified the differences between these SQL Ranking functions — let me know your thoughts in the comments section
Based on how you are framing your question, it seems that you currently don’t have “Data Analysis” Background but want to build a career in this field. Here are three things you could do:
Learn Tech Skills:You will need technical knowledge to be successful at analyzing data. SQL and Excel are a good starting point. You could do a lot with these tools — then depending on the bandwidth that you might have you could explore R. How do you learn this? Here’s a learning pathway: Learn #Data Analysis online – free curriculum ; Also search for free courses on Coursera or other platforms.
Learn Soft/Business Skills: This is as important as tech skills (if not more!) when it comes to Data Analysis. Finding Insights from your data is half the battle, you will need to put the insights in a context/story and influence business decisions and sometimes influence business change. we know change is always hard! So your soft/business skills will be very important. Also, you will benefit a lot from learning about how to break down problems, communicate your solution by using “business” language vs tech-speak.
Apply them (and keep improving):Now that you have picked up some tech and soft/biz skills, apply them! Get an internship, Help out a non-profit in your free time (Data Kind, Statistics Without borders, Volunteer Match are good resources to find a non-profit) and start applying your skills! It would also help you get some “Real” world experience and applying what you have learned while “learning-on-the-job” is arguably the BEST way to pick something up!
You have a SQL Server reporting services (SSRS) report that has a table which displays some records — but sometimes it can have NO rows; In that case, how to display “There are No rows” message so that it doesn’t confuse the consumer.
Open the report in SQL Server Data Tools and go to the “design” tab of your SSRS report
Select your table (do NOT select a cell inside a table. Make sure that the table is selected)
While the “table” is selected, Go the Properties section OR you can use F4
Inside the Properties section, find “No Rows” section and you should see a NoRowsMessage property:
Go to the preview tab to make sure it’s working and you should be ready to deploy the change!
I spend a lot of time writing SQL code — and as a reader of this blog, You might be in the same boat. So any productivity gains that we could get here could go a long way. On that note, here’s a quick productivity tip: Learn to comment/uncomment multiple lines of SQL code using keyboard shortcut.
If you are using SQL Server Management Studio, it’s “CTRL-K followed by CTRL+C” for commenting AND “CTRL+K followed by CTRL+U” for uncommenting.
If you are using some other Data Management Software tool, I am sure you can find it using their HELP section or googling around.
Either ways, these shortcuts go a long way in making you more productive! What is your favorite productivity tip?
How would get first/last transaction details for each user account?
Here’s a design pattern:
select AllTransactions.user_id,AllTransactions.purchase_amt from user_transaction_details AllTransactions
select user_id, min(transaction_timestamp) as first_transaction_timestamp from user_transaction_details
group by user_id
on AllTransactions.user_id = FirstTransaction.user_id and AllTransactions.transaction_timestamp = FirstTransaction.first_transaction_timestamp
To get the last transaction details for each user account, replace min function with max and that should be it.
Note: Depending on your data model and how you used it in the join, it might be that there would be multiple rows marked as “first/last” transaction and so would want to spend some time figuring out how to deal with these multiple row situation especially if you’re planning to further join this data.
In this post, I shared a design pattern to write a SQL query to get first/last transaction details for each user account type.
Question for you:
How would you solve this problem? Share you query in the comments section!
How do you customize the Legend Text on a chart? by default, it’s going to show you the name that you have in the Data Set, but sometimes that’s not what you want to display so how do you change the name?
It’s really useful when you don’t want to change the name of field in the dataset or when you are using an expression as an item on the chart and you need to display a business user friendly name on the report:
1. Go to Chart Data Properties:
2. To change the Legend Text of “Sales Amount CY” – Navigate to series properties of the “Sales Amount CY” series:
3. Go to “Legend” and enter the Text in the “Custom Legend Text“:
4. You can customize text for all legends on your report by navigating to the series properties.
In this post, I walked you through how you can customize the legend name/text in SQL Server Reporting Services.