The netstat is used for Network Monitoring and Troubleshooting. It stands for the Network Statistics. The netstat is a command-line network utility that displays: network connections for tcp, ud...

There are 3 redirects: Basically, when we run a command in terminal, belwo three files are created. Company File Descriptor Standard Input (stdin) ...

The software utility cron also known as cron job is a time-based job scheduler in Unix-like computer operating systems. Users who set up and maintain software environments use cron to schedule job...

Types of Permissions in Linux r: read w: write x: execute Permissions (rwx) levels u: current user g: group in which user belongs to o: others a: all How to chagne permissions...

chown: To change the user ownership Input: chown -c <user> <filename> Ouput: Changed the owner ship of the filename to the given user. chgrp: To change the group owner...

The top (table of processes) command shows a real-time view of the running processes in Linux and displays kernel-managed tasks. The command also provides a system information summmary that shows r...

ps stands for process status. This command is used to display all the running processes in the linux system. To display all the running processes in the current shell Syntax: ps [OPT...

Some process management commands in Linux jobs: Will show active jobs bg: Resume jobs to the background fg: Resume job to the foreground To resume a speciic jobs Syntax: ...

The kill command is used to terminate a process manually. Syntax: kill [OPTIONS] [PID] where, OPTION = signal name or no. PID = Process ID To see all the signal names Syn...

gzip and gunzip Command to zip a file Syntax: <br/> gzip <file_name> to unzip a file Syntax: <br/> gunzip <file_name> OR ...

In linux, a link is a connection between a file name and the actual data on the disk. We can also call it a shortcut. There are two types of links:- Soft Link and Hard Link Soft Link Links will be...

Linux Environment variable is a dynamic-named value, which may be used by one or more programs running. It can also be defined as a set of Rules and Values to build an environment. Syntax: VARIA...

Wildcards are characters that can be used as a substitute for any of a class of characters in a search. Suppose there are hundreds and thousands of files and we have to find only xml files then in...

Pipes are used to redirect a stream from one program to another program. The output of one command redirect it to the input of another. It allows us to combine multiple commands. Pipe Syntax We us...

grep stands for Global Regular Expression Print. This command is used to search for particular string or keyword from a file and print those lines matching a pattern in the shell. It checks line by...

A text editor which allows us to create and manipulate data in linux files. Most Common Kyes in VI Edidor i: Insert O: Insert on next line a: insert after a space Esc: Escape out of any m...

Everything in Linux is a File Even the basic commands that we use are stored as a file in the linux system. We can see where those files are located using the `whereis` command: For eg:- ``` Inpu...

Inside the linux terminal:- the $ represents the normal user the # represents the root or admin user To check the hostname we can use the hostname command For E...

In Python, a decorator takes a function and adds some functionality and returns it. Everything in python is an objects. In Python, everything is an object—yes, including classes. Simply said, name...

Nested Function When a function is defined inside another function, then it is called Nested Funciton. The Nested Function can access the variables of the enclosing scope. In Python, these non-ocal...

When builing up an iterator in Python, we have to do a lot of work like implementing a class with __iter__() and __next__() methods in a class, keep track of the internal states, and raise StopIter...

In Python, iterators are object that can be iterated upon. For an object to be an iterator it must have two special methods: __iter__ and __next__. In Python, iterators are used extensively. Whil...

Built-in classes can be used with Python operators. However, the same operator responds differently to several types. For instance, the + operator will combine two lists, concatenate two strings, o...

By using inheritance, we may create classes that inherit all the features of their parent classes and allow us to add new ones. Inheritance in Python Inheritance in python refers to defining a new...

Constructors In Python Class functions that begin with double underscore __ are called special functions as they have special meaning. The __init__() method is of great significance. Every time a ...

Object Oriented Programming Python, a multi-paradigm programming language supports several coding techniques. Making objects is one of the common ways to tackle a programming language. This is know...

Data Structures and Sequences Tuple A tuple is fixed-length, immutable sequence of Python objects. The easiest way to create one is with a comma-separated sequence of values tup = 4,5,6 tup Outp...

Getting Started with Pandas Pandas contains data structures and data manipulation tools designed to make data cleaning and analysis fast and easy in Python. While pandas adopts many coding idioms ...

Aggregation Framework The aggregation framework in its simplest form is just another way to query data in MongoDB. Everything we know how to do using the MongoDB query language (MQL) can also be do...

MQL Operators Update Operators: Example: $inc, $set, $unset These update operators enable us to modify data in the database. Query Operators: Query Operators provides additi...

Inserting New Documents Every MongoDB document must have unique _id value. ANd every _id field in a collection must have a unique value from the rest of the documents in the collection. Likewise, ...

How Does MongoDB Store Data? MongoDB uses documents to store data. When we view or update documents in the MongoDB shell, you’re working in JSON which stands for ‘JavaScript Standard Object Notati...

What is a MongoDB Database? A database, meaning a structured way to store and access data. More specifically, it is a NoSQL database. NoSQL databases mean that it doesn’t use the traditional appro...

sql2csv : documentation sql2csv: executes an SQL query on a large variety of SQL databases (e.g. MS SQL, MySQL, Oracle, PostgreSQL, Sqlite) outputs the result to a CSV ...

What is csvkit? csvkit: is a suite of command-line tools is developed in Python by Wireservice offers data processing and cleaning capabilities on CSV files ...

What is curl? curl: is short for Client for URLs is a Unix command line tool transfer data to and from a server is used to download data from HTTP(S) sites ...

Assigning Variables Similar to other languages, you can assign variables with the equal notation. var1='Moon; Then reference with $ notation. echo $var R...

Why Bash Scripting? (Bash) Bash stands for ‘Bourne Again Shell’ Developed in the 80’s but a very popular shell today. Default in many Unix systems, Macs AWS, Google, ...

Deleting Table and View Triggers DROP TRIGGER PreventNewDiscounts; Deleting Database Triggers DROP TRIGGER PreventNewDiscounts; DROP TRIGGER Preven...

Advantages of Triggers Used for database integrity Enforece business rules directly in the database Control on which statements are allowed in a database Implem...

Definition and properties Performs a set of actions when fired The actions are performed only after the DML event is finisehd Used with INSERT, UPDATE, and DELETE sta...

What is a trigger? Special type of stored procedure Executed when an event occurs in the database server Types of Trigger(based on T-SQL commands) ...

Data Imputation Divide by zero error when calculating Avg Fare/TripDistance EDA uncovers hundreds of TaxiRide trip records with Trip Distance = 0 Data Imputation meth...

What is a stored procedure? Routines that Accept input parameters Perform actinos (EXECUTE, SELECT, INSERT, UPDATE, DELETE, and other SP statments) Return status ...

What are User Defined Functions (UDFs)? User Defined Functions (UDFs) are routines that can accept input parameters perform an action return result (single scalar...

Temporal EDA Exploratory Data Analysis (EDA) Process Iterative No specific checklist for EDA questions SQL function...

What is concurrency? Concurrency: two or more transactions that read/change shared data at the same time. Isolate our transaction from other transactions Transaction isolation...

Transactions What is a transaction? Transaction: one or more statements, all or none of the statements are executed. Example: Transfer $100 ...

Raise Error Raise Errors Statements RAISERROR THROW Microsoft suggests THROW RAISEERROR ( {msg_str | msg_id | @local_variable_message}, seve...

Datasets Products Table Buyers Table Staff Table Orders Table Getting an error CONSTRAINT unique_product_name UNIQUE(product_name); INSERT INTO products(product_name, sto...

Granting and revoking access to a view GRANT privilege(s) or REVOKE privilege(s) ON object TO role or FROM role Privileges: SELECT, INSERT, UPDATE, DELETE, etc. Obe...

In a database, a view is the result set of a stored query on the data, which the database users can query just as they would in a persistent database collection object. Virtual table that is n...

Star and Snowflake Schema Star Schema Dimensional modeling: star schema Fact tables Holds records of a metric Changes regularly Connects to dimensions via forei...

How should we organize and manage data? Schemas: How should my data be logically organized? Normalization: Should my data have minimal dependency and redundancy? View...

COUNT() Returns the number of items found in a group. COUNT([ALL] expression) COUNT(DISTINCT expression) COUNT(*) Example: SELECT ...

Position Functions LEN() CHARINDEX() PATINDEX() LEN() Returns the number of characters of the provided string. Syntax: LEN...

Common mistakes when working with dates and time Inconsistent date time formats or patterns Arithmetic Operations Issues with time zones Time Zones in...

Categories of Data Types Exact numerics Approximate numerics Date and Time Character Strings Unicode Character Strings Binary Strings Other da...

Using Aggregation Functions Over Windows Ranking Functions ROW_NUMBER(): Unique, ascending integer value starting from 1. RANK(): Ascending integer value starting from 1. ...

Key Aggregation Functions Counts COUNT() COUNT_BIG() COUNT(DISTINCT) Other Aggregates SUM() ...

Dates from parts DATEFROMPARTS(year,month,day) TIMEFROMPARTS(hour, minute, second, fraction, precision) DATETIMEFROMPARTS(year, month, day, hour, minute, seconds,ms) ...

Building Dates Building a Date SELECT GETDATE() AS DateTime_LTz, GETUTCDATE() AS DateTime_UTC; SELECT SYSDATETIME() AS DateTime2_LTz,...

Grouping data in T-SQL SELECT SalesPerson, SalesYear, CurrentQuota, ModifiedDate FROM SaleGoal WHERE SalesYear = 2011 ...

Using Variables in T-SQL Variables are needed to set values DECLARE @variablename data_type Must start with the character @ Vari...

Examining Totals with Counts SELECT COUNT(*) FROM Incidents The above sql statments returns the total number of rows in the Incidents table. Count w...

Exploring Data With Aggregation Reviewing summarized values for each column is a common first step in analyzing data If the data exists in a database, fastest way to aggreg...

Implementing relationships with Foreign Keys A Foreign Key (FK) points to the Primary key (PK) of another table. Domain of FK must be equal to the domain of PK Each v...

What is a Key? Attribute(s) that idenfity a record uniquely As long as attributes can be removed: superkey If no more attributes can be removed: minimal superky or ke...

Integrity Constraints Attribute Constraints, e.g data types on columns Key Constraints, e.g primary keys Referential Integrity Constraints, enforced through foreign k...

Using information schema SELECT table_schema, table_name FROM information_schema.tables; Taking the look at the columns of a ...

CRUD OPERATION CREATE Databases, Tables or Views Users, prermissions and security groups READ Example: SELEC...

PRIMARY KEYS: A primary key is used to ensure data in the specific column is unique. It is a column cannot have NULL values. It is either an existing table column or a column that is speci...

SUM It is used to calculate the total amount of a column. Example: SELECT SUM(affected_customers) AS total_affec...

A SQL Server is a relational database system developed by Microsoft. And a Transact-SQL (T-SQL) is a Microsoft’s implemenataion of SQL butwith added functionality. Queries SELECT ...

Convolutional Neural Networks (CNN/ ConvNet) A Convolutional Neural Network, also known as CNN or ConvNet, is a class of neural networks that specailizes in processing data that has a grid-like to...

What is Backpropagation? Backpropagation is a supervised learning algorithm, for training Multi-layer Perceptrons (Artificial Neural Networks).It refers to the method of calculating the gradient o...

To understand the concept of the architecture of an artificial neural network, we have to understand what a neural network consists of. In order to define a neural network that consists of a large ...