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DML Command Insert Command Its used to insert the record into table example- Command for inserting single record insert into <table name> values(value1, value2...) Command for inserting multiple command at a time insert into <table name> values(&col1, &col2...., &coln); whenever you enter query like this it will ask you to like this - enter a value for column1- value1.. and then hit enter  - enter a value for column2- value2.. and then hit enter - enter a value for column3- value3.. and then hit enter Now it will show 1 row created  if you want to create more record use / and hit enter SQL> /   hit enter // it will Execute most recent query again //this will so again and so on... - enter a value for column1- value1..  and then hit enter  - enter a value for column2- value2..  and then hit enter - enter a value for column3- value3..  and then hit enter // if you will miss any value here that will be inserted as NULL value Update command Used to upda

Make admin panel with Active admin rails || active_admin rails  Open Terminal and copy and paste this Command rails new admin_example // creating new rails application go inside the project cd admin_example run bundle install bundle install open your gem file and add this new gem's gem 'activeadmin' / / for active admin panel gem 'inherited_resources' //  making your controllers inherit all restful actions gem 'devise' // for user authentication  run bundle install again bundle install install active admin rails g active_admin:install / /install active admin to your project migrate database rake db:migrate check your seed file and run rake db:seed create user file and model rails g User name email  create post file and model rails g Post title body:text published_at:datetime user:references Now Migrate DataBase rake db:migrate start rails server rails s Hit url localhost:3000/admin/login Enter login details you can find login

Redirect site http to https  There are two ways to redirect http to https Open your nginx Server Configuration file server {     listen 80 default_server;     server_name _;     return 301 https://$host$request_uri; } Open your production.rb file and copy and paste this line config.force_ssl = true  For Redirect Http to https you must have to add SSL Certificate in your site if you add SSL certificate to your site Https will be bordered with Green colour in url of site if you did not add  SSL certificate to your site Https will be bordered with Red colour in url of site(same in case if your SSL Certificate Expire)

Convert string value into fractional self.try(:shipping).fractional.to_f   // this will convert string value to fractional example- if  self.try(:shipping)  =>   #<1500 Euro shiiping> then   self.try(:shipping).fractional.to_f will return 1500

How to locate nginx configuraion file on server login to server on console  cd /etc/nginx/ sudo nano nginx.conf if does not locate cd /usr/local/nginx/conf/ sudo nano nginx.conf or try this too cd /usr/local/etc/nginx/ sudo nano nginx.conf

How to login on sever from console ssh ssh user@server_address and press enter. example- server 'abc.rahul.com', user: 'your_user_name', roles: %w(app web db), primary: true t his is your config/environments/production.rb file then your command will be  ssh  your_user_name@abc.rahul.com

Rational Number or Rational Mothod in ruby or Rational operation Rational Number is always comes with paired integer Number(1 ,2 ,3 .... && -1, -2, .....) x/y (where y>0). Rational (1) => (1/1) Rational (2, 5) =>(2/5) Rational(4, -8) => (-1/2) 5.to_r =>(5/1) 2/3r => (2/3) Rational into Numeric rational*numeric -> numeric (perfoms multiplecation) Rational(1, 3)  * Rational(2, 3)   => (2/9) Rational(200)   * Rational(1)      => (200/1) Rational(-5, 4) * Rational(-4, 5)  => (1/1) Rational(9, 4)  * 4                => (9/1) Rational(20, 9) * 9.8              => 21.77777777777778 rat ** numeric => numeric (Performs exponentiation) Rational(3)    ** Rational(3)    => (27/1) Rational(10)   ** -2             => (1/100) Rational(10)   ** -2.0           => 0.01 Rational(-4)   ** Rational(1,2)  => (1.2246063538223773e-16+2.0i) Rational(1, 2) ** 0              => (1/1) Rational(2,

Install Adobe Flash plugin Open terminal copy and paste it sudo apt-get update Now copy and paste sudo apt-get install adobe-flashplugin Un-Install Adobe Flash plugin Open terminal copy and paste it sudo apt-get update Now copy and paste sudo apt-get remove adobe-flashplugin

Un-Install Google Chrome in Ubuntu 16.04 || 14.04 Open terminal. Copy and paste command sudo apt-get purge google-chrome-stable copy and paste this sudo apt-get autoremove Chrome Successfully Removed from system

Install Google Chrome in Ubuntu 16.04 || 14.04 Open terminal. Copy and paste command wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add - copy and paste this sudo sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list' Now install Chrome Browser sudo apt-get update sudo apt-get install google-chrome-stable launch Google Chrome google-chrome

Difference Between select and collect Select & collect select return array of hash of all field into a table Example user.select(:id) // it will return all fields with id user.all.collect(&:id) // it will array of id's

Difference Between pluck and collect Pluck Pluck takes less time then collect because when we use collect we have to execute two queries for collecting record Example-  When have a user table and we have to collect all id's User.all.collect(&:id) // when we use collect we are running two query internally                                        first user.all and then we collect id's User.pluck(:id) // Here we are running only one query that's why it take less time Pluck also take more than one parameter at a time but collect can not Example- user.pluck(:id, :name) // it will return array of id and name user.collect(&:id , &:name) // it will give an error

Skip Generating Views and Helpers in rails When we generate Controller in rails rails generate controller user index  --no-helper --no-assets --no-controller-specs --no-view-specs By this command you can only generate user controller and skip helpers and views and assets too 

DDL Command CREATE Command It is used to create any data base object like tables, views, indexes, sequences, synonyms , users, functions, procedures, triggers, packages and so on. HOW TO CREATE A TABLE?            syn: CREATE TABLE <table_name>             (              <colname1> DATATYPE (size),               <colname2> DATATYPE (size),                : : : :,                : : : :,             ); INSERT Command This command is used for inserting new records into the tables          Syntax:           INSERT INTO <table_name>[(col1, col2,...., col n)]           VALUES(val1, val2,.....,val n);                  NOTE:  i) If number of columns in the table and number of values inserting in to the table      are equal, then no need to specify column names while inserting records.            ii) Char, Varchar2 and date type values should be enclosed in Single Quotes.            iii) If Number of inserting values are less than the

DATATYPES IN SQL  The data type represents the type of data to be entered into a column and Db engine can assign memory for thevalue entered into the column. There are 5 types of DataType in sql. String DataTypes Numeric DataTypes Date Datatypes Binary DataTypes LOB--Large Objects String Data Types These data types support sequence of character, digits and any symbol from keyboard. CHAR(size) It is used to store fixed length character strings. By default the size is 1 character, and max size is 2000 chars orbytes. Ex: student_id, email, address and so on VARCHAR2(size) It is used to store variable length character strings. No default size. we should specify size and max size is 4000 chars /bytes. Ex: emp names, addresses, descriptions, city names. LONG It is used to store variable length char data(similar to varchar2 data type) but max size is 2 GB NOTE: Only one long type column is allowed per a table. 1) NUMBER(Precision, [Scale])    It is used to store numb

Naming Convention in SQL Rules to follow before specifying names(Object names, Column Names and Variable Names). Each name should begins alphabet Valid character set is a-z,A-Z,0-9,@,$,# and _ (underscore) Ex:  Emp123   Emp_o11 Names are not case sensitive Already existed names are not allowed Pre defined keywords (ReservedWords) are not allowed as names. Blankspace within a name is not allowed Max length of any name is 32 chars

Types of SQL commands 1) DDL(data definition language) commands:       Used to create or change or delete any data base objects CREATE ALTER DROP TRUNCATE RENAME 2) DML(data manipulation language) COMMANDS       Used to fetch data / enter new data/ changing existed data / deleting the data from table. INSERT  UPDATE  DELETE  TRUNCATE 3) DRL(dataretrieval language) Command     SELECT (logicalcommand) 4) DCL(DATA CONTROL LANGUAGE) COMMANDS     Used to control the access of data base objects. These commands are used by DBA (databaseadministrator) GRANT  REVOKE 5) TCL(TRANSACTION CONTROL LANGUAGE) COMMANDS      Used to save or cancel the actions/transactions made on table data. COMMIT  ROLLBACK  SAVEPOINT

Features of Sql * Plus At a time only one query is allowed to execute Sql queries are not case sensitive Each query is terminated with ; ( semi colon ) SQL commands are ANSI standard ( American National standard institute )

Structured query language It is a collection of pre defined commands and constructs with syntactical rules. 1. Sql is a client tool to interact with ORACLE DB /any DB 2. Sql is to be installed in to the system whenever we have installed the db software. 3. Client [Technical] requests should be submitted in the form of "Queries". 4. Queries are executed by SQL STMT EXECUTOR ( Oracle Db Engine ) 5. Queries are executed against database and output will be displayed on the Sql * plus window.

What is sql in Deep(Structured query language) Oracle was the first company to release a product that used the English-based Structured Query Language, or SQL. This language allows end users to extract information themselves, without using a systems group for every little report. Oracle’s query language has structure, just as English or any other language has structure. It has rules of grammar and syntax, but they are basically the normal rules of careful English speech and can be readily understood. What is SQL QUERIES It is known as data base language. It is used to communicate with any database. We can use this language constructs to write SQL QUERIES. What is SQL* PLUS SQL * PLUS is a default client tool and acts as an interface between client and database. What is SQL It is a collection of pre defined commands and constructs with syntactical rules

 Export Import component in react See installation and configuration in my other blog Now Create a file into a public folder or anywhere into Root directory inside your project folder Create to directory into root directory         mkdir public           mkdir src Create two new into public folder index.html index.js Create two new file into src folder main.js  item.js Copy and paste code into index.html <!DOCTYPE html> <html> <head> <title>React - demo</title> </head> <body> <div id="root"></div> <script src="index.js"></script> </body> </html> Now into item.js import React from 'react'; class Item extends React.Component{ render(){ return( <div> Hello Item </div> ); } } export default Item; // you must have to make component exportable Now into main.js import React from 'react&#

Install Webpack and configure it first See installation and configuration in my other blog Now Create a file into a public folder or anywhere into Root directory inside your project folder Create to directory into root directory         mkdir public           mkdir src Create two new into public folder index.html index.js Create a new file into src folder main.js Copy and paste code into index.html <!DOCTYPE html> <html> <head> <title>React - demo</title> </head> <body> <div id="root"></div> <script src="index.js"></script> </body> </html> Now into main.js import React from 'react'; import ReactDOM from 'react-dom'; function Welcome() { return (<div> Hello </div>) } const root = document.getElementById('root');  ReactDOM.render(<Welcome />, root); Project Structure will be like this

Install Webpack and configure it first See installation and configuration in my other blog Now Create a file into a public folder or anywhere into Root directory inside your project folder Create to directory into root directory         mkdir public           mkdir src Create two new into public folder index.html index.js Create a new file into src folder main.js Copy and paste code into index.html <!DOCTYPE html> <html> <head> <title>React - demo</title> </head> <body> <div id="root"></div> <script src="index.js"></script> </body> </html> Now into main.js import React from 'react'; import ReactDOM from 'react-dom'; class Welcome extends React.Component{ render(){ return( <div> Hello  </div> ); } } const root = document.getElementById('root');  ReactDOM.render(<Welcome />, root);

WARNING in configuration The 'mode' option has not been set, webpack will fallback to 'production' for this value. Set 'mode' option to 'development' or 'production' to enable defaults for each environment. You can also set it to 'none' to disable any default behavior. Learn more: https://webpack.js.org/concepts/mode/ module.exports = {   mode: "development", // Add mode here to solve this warning    entry: './src/main.js', // Bundle all assets from this location together    output: {        filename: 'index.js', // Output to this file        path: path.resolve( __dirname, 'public' ), // In this location    }

Run this commands form terminal or cmd npm init npm i webpack --save-dev npm i webpack-cli --save-dev  npm install -D babel-loader @babel/core @babel/preset-env webpack  npm i @babel/preset-react --save-dev npm i babel-core --save-dev npm i babel-preset-env --save-dev npm i babel-preset-es2015 babel-preset-react babel-preset-stage-0 --save-dev npm i react react-dom --save-dev npm install webpack-dev-server -g   // In window and mac os this command will not work then use this npm i webpack-dev-server --save-dev Create a new file named Webpack.config.js into root directory copy and paste this code into webpack.config.js file var path = require('path'); module.exports = {    entry: './src/main.js', // Bundle all assets from this location together    output: {        filename: 'index.js', // Output to this file        path: path.resolve( __dirname, 'public' ), // In this location    },    module: {        rules: [        

Give mode in webpack.config.js            mode: "development || production"  //whatever you want to give Use it before Entry module.exports = {   mode: "development",    entry: './src/main.js', // Bundle all assets from this location together    output: {        filename: 'index.js', // Output to this file        path: path.resolve( __dirname, 'public' ), // In this location    }, 

Create a directory into your local         for windows            mkdir react-demo         for linux                       mkdir react-demo Go to directory             cd react-demo Type npm init            for installing node and creating package.json file npm i webpack --save-dev           create dependency by webpack npm i webpack-cli --save-dev           This cmd is used to create dependency for webpack-cli in package.json file.           Like -             "devDependencies": {            "webpack": "^4.16.2",            "webpack-cli": "^3.1.0"             } npm install -D babel-loader @babel/core @babel/preset-env webpack "devDependencies": {    "babel-core": "^6.26.3",    "babel-loader": "^7.1.5",    "babel-preset-env": "^1.7.0",    "webpack": "^4.16.2",    "webpack-cli":

Webpack is a tool that puts all your assets including images,javascript ,fonts and css in a dependency graph entry point: is the file webpack looks for to start building your Javascript bundle webpack’s main strength is code splitting. It introduce a production mode and development mode. As ,, Syntax of  ReactJS is based on ES6. old browsers doesn’t understand ES6. So , to run JS we need something which transform our ES6 code to browser understand language , the same thing is done by babel-loader. Babel-loader is a webpack loader for transpiling ES6 and above , down to ES5. For this, you need three things - babel-core, babel-loader, babel-preset-env   Commands- 1. npm init: This cmd create a package.json file . 2.npm i webpack --save-dev: This cmd generate dependencies for webpack in package.json file. Like "devDependencies": {    "webpack": "^4.16.2"  } 3. npm i webpack-cli --save-dev : This cmd is