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SQL Query: 3 Methods for Calculating Cumulative SUM

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 Explain String Immutability in Python Correctly

Here is an answer to explain the immutability of Strings in Python. It means that you can't modify the string. Due to this, you can use strings securely in many places of your project.

Strings Immutability

How to check string immutability

Here is an example. In the python shell, assign a value of your choice to a string. Here my choice is ABCD, and I have assigned it to myString. I have tried to replace A with Z. But, it gave an error due to the immutability of strings.

>>> myString = 'ABCD'
>>>myString [0] = 'Z'

What is learning here

The strings immutability is an interview question. In interviews, you can say that strings are immutable, and you can't replace its data.

Benefits of strings immutability

  1. It saves a lot of time since the data in strings are immutable. It results in high performance.
  2. String objects you can reuse as no one can modify its value.
  3. Strings are elemental. So no activity can change its value ( these are more like numbers).



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