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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

How to Use List Function in Python

Here's is an answer to calculate the length of the repeated lists. LIST is a principle data type in Python that holds a list of values. Usually strings.

List() Function the Real Usage

You can do various operations with Lists. The best examples are REPEAT, APPEND, INSERT, EXTEND, COUNT. Still more you can do.


Note: This question is from a test recently held by an HR company. HR firms usually ask to take an online test to filter the job-seekers.

You can find list length using list() and len() functions


IN THIS PAGE


1. Question
2. How to Find Length


Interview Question 

The '* 2' says times the list is repeated. In this question, they have given '2' times.


my_list = ['srini', 'seetha', 'rao']
b = len(list(list(list(list(list(my_list*2))))))
Print (b)


Select Answer

1. 5
2. 6
3. 7
4. None

Explanation:

  • In the first step, the '*' says, you repeated the List two times.
  • It confuses the test-taker since they have given multiple functions of the list().

How to get Length


You can code the way I did. So that you can get the length correctly. So, the answer to the question is '6'. The List is repeated twice. There's no effect of multiple lists on the list.


Result (Ubuntu Linux OS)


At the command level, the given question entered. After pressing enter, it showed the result as '6'. That means the list (which has initially '3' elements') doubled. So the list length is now '6'.


Result of Python List

References

  1. Here're the best examples on Python List
  2. Here's the complete list for your reference.

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