Category Archives: CS Courses

OOP Topics Need To Cover

OOP in C#





SOLID Concepts

Object Oriented Programming Concepts

OOP Clear

Training Set, Validation Set, Test Set

Training Set is a subset of the dataset used to build predictive models.
Validation Set is a subset of the dataset used to assess the performance of model built in the training phase
– It provides a test platform for fine-tuning model’s parameters and selecting the best performing model
– Not all modeling algorithms need a validation set
Test set or unseen examples is a subset of the dataset to assess the likely future performance of a model.
– If a model fits the training set much better than it fits the test set. Overfitting is probably the cause


Binary Classification(two class classification)

true|false, 1|0, -1|+1, male|female

Multi-class classification problems can be seen as binary classification problems.

Model Evaluation:

PHP OOP Project

Basic Simple Project By Me:

By Others:
From OOP Fundamentals udemy Video project:


PHP OOP: Class, Method, Object, Instance, Declare, Echo, Inheritance,Constructor,Access Control,Static!

PHP OOP example described here from edwin’s video:

Inheritance example:


Access control: Public, Private, Protected

Static Data in Class:


Database Interview Questions

Theory site:
Another Resource:

SQL Join – Interview Clear

In below:  The relationship between the two tables is specified by the customer_id key, which is the “primary key” in customers table and a “foreign key” in the orders table:

customer_id first_name last_name email address city state zipcode
1 George Washington [email protected] 3200 Mt Vernon Hwy Mount Vernon VA 22121
2 John Adams [email protected] 1250 Hancock St Quincy MA 02169
3 Thomas Jefferson [email protected] 931 Thomas Jefferson Pkwy Charlottesville VA 22902
4 James Madison [email protected] 11350 Constitution Hwy Orange VA 22960
5 James Monroe [email protected] 2050 James Monroe Parkway Charlottesville VA 22902
order_id order_date amount customer_id
1 07/04/1776 $234.56 1
2 03/14/1760 $78.50 3
3 05/23/1784 $124.00 2
4 09/03/1790 $65.50 3

Note that (1) not every customer in our customers table has placed an order and (2) there are a few orders for which no customer record exists in our customers table.

Inner Join Query:


first_name last_name order_date amount
george washington 07/04/1776 $234.56
john adams 05/23/1784 $124.00
Thomas Jefferson 03/14/1760 $78.50
Thomas Jefferson 09/03/1790 $65.50






Good Learning Site for beginners:


Less Important But Okay:

Data Science MOOC (Will do someday)

Data Science: Discrete vs Continuous

Making Predictions with WEKA

How to Save Your Machine Learning Model and Make Predictions in Weka

Decision Tree