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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 Work with 'Pointers' in Python

Pointers denote an address (memory location). It has three identities - Name, Value, and Location (Address). Python doesn't support pointers as-is. You need to import 'ctypes' package to work with C Language.

Note: Pointer is popular in C, C++. The called module just uses the value of Pointer (not address).  Below is my detailed post on pointers.  


An article on how to work with pointers


How to work with Pointers

  • To pass a reference(address) to the C interface.
  • You can use C Language in Python by importing 'ctypes.' 

Pointer Notation

1. Value
2. Address
3. Name

Python Pointers


Python doesn't support pointers. C and C++ extensively support pointers. Pointer is nothing but an ADDRESS. It is immutable. That means you can't change the value. Python supports pointers for the purpose to interact with C Language.



Pointers

How to Import 'ctypes'

  1. Import 'ctypes' library for the purpose of working with C language. 
  2. Here's how to import 'ctypes' for windows and Linux.

How to denote Pointers

Here's the way to denote pointers in Python. Check out here Python Pointers.

 
from ctypes import * 
i = c_int(42) 
pi = pointer(i) 


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