Understand Statistics in SQL Server for better performance troubleshooting 

Glad it was helpful!

Sure. I will work on this. This is interesting for me! Thank you.

Sure, will do. I have a plan on this and started working on it :)

@@arslanov1886 :: Appreciate your hard work bro :) Thank you !

I do not think statistics is restricted to one 8K page as they are BLOBs learn.microsoft.com/en-us/sql/relational-databases/statistics/statistics?view=sql-server-ver16#statistics-1 Regarding difference, I highly recommend watching my video from 6:56 specifically as I explained how statistics help to choose best way to run the query. Let me explain in this way: You have following indexes: Index A Index B Index C You are starting to run a query to retrieve RowsA. In this case, what SQL Server does firstly is, to find the best( less-costly) way of getting these rows. For this, it should evaluate several options like below: 1. Run query with Index A (e.g. in this case SQL Server has to go through only 100 rows to retrieve RowsA) 2. Run query with Index B (e.g. in this case SQL Server has to go through only 120 rows to retrieve RowsA) 3. Run query with Index C (e.g. in this case SQL Server has to go through only 160 rows to retrieve RowsA) 4. Run query without any index (e.g. in this case SQL Server has to go through all 1000000 rows to retrieve RowsA) As can be seen, SQL Server chooses first option with Index A as it is less costly (it should work with less rows in this case). In this case, statistics help SQL Server to predict how many rows are expected to go through beforehand to choose the best option which is 100 rows in our first case. As you can see, if we take index as a route to reach destination, statistics is "prediction of costs" if we choose this specific route in terms of number of rows.

Btw, Greetings from Japan!

@@arslanov1886 Thank you for taking so much time to explain. After some thinking and hitting the wall with my head :) may I bring my words in addition ? Please tell me if I am wrong. So statistics helps to find / allocate the data and predict the number of rows that would come. Then the SQL Server makes the decision whether it can use an index or not to collect the data. Are you Japanese ? I mean you could be just working and living there. Big Thank you.

Correct. Yes, I am just living and working here in Japan :)

@@arslanov1886 All right. Thank you. For a moment I thought I asked something inappropriate. I love learning about Japan. It is so unique and exotic in many ways compared to the western world. I have many things to sort out now but some day I will look for you in LinkedIn and ask you if you would have time share some of your insights.