Querys in Ruby on Rails

Query's in Ruby 

  In this post we discuss about how to retrieve  data from database like mysql or sql ...

     Select

 

        Model.where("column = ? , value)

        Model.where("column = ? or other_column = ?", value, other_value)

        Model.where("column = ? and other_column = ?", value, other_value)

Rails Time/Date Formats (strftime)

Rails Time/Date Formats (strftime)

Method:

               <%= @contact.created_at.strftime("%d/%m/%Y")  %>


 Year
%Y     year with century 2007
%y     year without century 07
%C     century number (year divided by 100) 20
Month
%B     full month name January
%b     abbreviated month name Jan
%h     same as %b Jan
%m     month as number (01-12)
Week
%U     week number of the year, Sunday as first day of week (00-53)
%W     week number of the year, Monday as first day of week (00-53)
Day
%A     full weekday name Wednesday
%a     abbreviated weekday name Wed
%d     day of the month (01-31)
%e     day of the month, single digits preceded by space ( 1-31)
%j     day of the year (001-366)
%w     weekday as a number, with 0 representing Sunday (0-6)
%u     weekday as a number, with 1 representing Monday (1-7)
Time
%H    hour (24-hour clock) (00-23)
%k     hour (24-hour clock); single digits preceded by space ( 0-23)
%I     hour (12-hour clock) (01-12)
%l     hour (12-hour clock); single digits preceded by space ( 1-12)
%M     minute (00-59)
%S     seconds (00-59)
%p     either AM or PM AM
%Z     timezone name or abbreviation EDT
%z     timezone offset from UTC -0400

Ruby installation and create application

Ruby on Rails

Installation:

• Rails-3.2.11
• Ruby 1.9.2

 Ruby Installation:

•   curl -L https://get.rvm.io | bash -s stable
• --bash -sk stable < <(curl -sk                  https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)
• [[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"
• rvm install 1.9.2(if you need 1.9.3  you change 1.9.3)

Rail instalation:

                            gem install rails r=3.2.11

Create New Project:

           step 1 -->[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"

           step 2 -->rvm --create use1.9.2@name(gemset give any name)

           step 3--> rails new blog(projectname)

   step 4--> rm -rf Gemfile.lock

          step 5->change gem 'mysql2' in GemFile

           step 6-->bundle install(used for maintain rail version)

-->Exception

An error occurred while installing mysql2 (0.3.11), and Bundler cannot continue.

Make sure that `gem install mysql2 -v '0.3.11'` succeeds before bundling.

-->Solution

       sudo apt-get install libmysqlclient-dev

          step 7--> rake db:create

Exception:

                      Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes.

solution

-->gem install execjs

        step 8--> rails g scaffold Question(give your application name any name) title:string             

                      questions:string answers:string(field name)

                                                                       rails      mysql or other

:binary     blob

         :boolean    tinyint(1)

:date     date

:datetime   datetime

:decimal    decimal

:float   float

:integer    int(11)

:string     varchar(255)

:text     text

:time     time

:timestamp  datetime

step 9-->-->rake db:migrate

step10-->rails server

       step 11:open browser type url localhost:3000/ blog (projectname)

   if  you add model or controller to your application follow below instruction 

      model

                 rails g model User(modelname)

      controller

                 rails g controller User (controller name)

      mailer
                rails g mailer  user_mail(mailer name)

      migration 
             scaffold
               rails g scaffold Question(give your application name any name) title:string          

                      questions:string answers:string(field name)

       add new-column

                    rails g migration add_fieldname_to_tablename  fieldname:string