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SQL Query: 3 Methods for Calculating Cumulative SUM

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SQL provides various constructs for calculating cumulative sums, offering flexibility and efficiency in data analysis. In this article, we explore three distinct SQL queries that facilitate the computation of cumulative sums. Each query leverages different SQL constructs to achieve the desired outcome, catering to diverse analytical needs and preferences. Using Window Functions (e.g., PostgreSQL, SQL Server, Oracle) SELECT id, value, SUM(value) OVER (ORDER BY id) AS cumulative_sum  FROM your_table; This query uses the SUM() window function with the OVER clause to calculate the cumulative sum of the value column ordered by the id column. Using Subqueries (e.g., MySQL, SQLite): SELECT t1.id, t1.value, SUM(t2.value) AS cumulative_sum FROM your_table t1 JOIN your_table t2 ON t1.id >= t2.id GROUP BY t1.id, t1.value ORDER BY t1.id; This query uses a self-join to calculate the cumulative sum. It joins the table with itself, matching rows where the id in the first table is greater than or

Tail Command in Linux: A Comprehensive Overview

The tail in Linux is handy command. You can check the last lines of a file in Linux/Unix operating systems.

You can use it to display last lines from single file, display last lines from multiple files, display the last entries of log files.


Tail Command in Linux


During production support the usage of Tail command is helpful since you can check latest logs quickly. Here are the top Tail command examples.

#1 Display last lines in a file (Tail file Linux)


Here's the tail command that shows last three lines of a file.

cat sample.txt | tail -3

It displays last 3 lines of a file. The same command you can use as

tail -3 sample.txt

#2 Display last lines of multiple files


There are three files. sample2.txt, sample3.txt, sample4.txt. The command displays the last 3 lines from all the three files.

tail -3 sample[2-4].txt


Tail command


#3 Tail -f option (Tail f Linux)


The –f option is to check status of long-running process that is redirecting output to a file. For example, if you invoke the below command, the status it writes to the output.

find . -print |xargs grep -i abc </tmp/abc &

Using the -f option you can see contents of the file /tmp/abc whenever it is updated: 

tail -f /tmp/abc


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