The most useful Rails 4 commands

These are some useful rails commands:

• rails -v: Gets the rails version.
• rails new: Generates the  application skeleton  and base files. (e.g rails new myBlog)
• rails dbconsole: shows the database that  is currently on your system .
• rails s or rails server: launches the web server (webrick)
• rake db:migrate: Runs the migrations files that have not been run.
• rails generate model: Creates the model and will create a migration file
• rails generate controller: creates the controller in your application
• rails generate model your_model_name --skip-migration: Generates the model but will not create the migration file.
• rails generate migration : creates a migration file.
• rails d migration your_migration_name:removes the migration file specify
• rake db:rollback: roll back the most recent migration
• rake routes:  Displays all routes configured in your rails application

MYSQL Save the Last Id Inserted in a Variable

To save the last id inserted in a SQL variable , we need to do this:

INSERT INTO Users (user_name, user_email, user_address, user_city)
VALUES ('bryan.hamilton','Tbha@gmail.com','Av.21','ohio'); 

//we create a new variable called userLastId
 SET @userLastId = LAST_INSERT_ID( );

//now, we can use this varable in another sql sentence

INSERT INTO articles (art_title, art_body, art_user_id, art_created_at)
VALUES ('Geologic time scale','my body ..',@userLastId ,NOW());  

 

Basically, when you save the last id inserted in the variable that value is available to use it in others SQL sentences.

Phenomenon Disaster Videos

Home Destroyed by Furious Australia Storm

Tornado Disaster 

Convert a date into Timestamp in Javscript

To convert a date into timestamp milisecond  in JavaScript we are going to use the function new Date() that JavaScript provide  to deal with dates.

Basically, this is code:

//convert date into a timestamp milisecond
var oDate = new Date('2015','05','12','07','30','00');

//printing the timestamp   
console.log(oDate.getTime());

Explanation:

The function  Date() , receives the following parameters:
new Date(year, month, day, hours, minutes, seconds, milliseconds)

so,the Object oDate(Variable) has a method called getTime, that you can access to convert the date into a timeStamp.


Output:

1434115800000


NOTE: In javascript, the conversion to timestamp is in timestamp millisecond and not timestamp epoch. 

Regular Expressions You Should Know(REGEX)

In this section, I will be writing some REGEX that could be helpful  to your  projects.



REGEX #1: Numbers Separated by comma or blank spaces.Example(1,2 ,3  ,4)

   //Numbers Separated by comma or blank spaces
   ^[\d]{1,}(\s*,\s*[\d]{1,})+$
 
 

REGEX #2:  Only number

   //Only Number
   ^(\d)+$
 
 

REGEX #3: Alphanumeric

   //Only Alphanumeric 
   ^(\w)+$
 
 

REGEX #4: Validate URL (either http, https or IP number)

   //Validate URL (either htpp,https or IP number)
   ^(http|https):\/\/([\w+?\.\w+])+([a-zA-Z0-9\~\!\@\#\$\%\^\&\*\(\)_\-\=\+\\\/\?\.\:\;\'\,]*)?$
 
 

REGEX #5: Validate Emails. Example : myUser.test01@gmail.com

   //Validate emails
   ^[\w_.+-]+@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$
 
 

REGEX #6: Validate Hours format

//Validate Hours Format
^[\d]{1,2}:[\d]{1,2}:[\d]{1,2}$

REGEX #7: Validate date format

//Validate date Format
^[\d]{2}\/[\d]{2}\/[\d]{4}$

REGEX #8: Validate IP number format (IPV4)

//Validate IP number format (IPV4)
^[\d]{1,3}.[\d]{1,3}.[\d]{1,3}.[\d]{1,3}$

REGEX #9: Regular expression to limit number of characters to 10

//Limit number of characters to 10
^[a-zA-Z]{1,10}$

REGEX #10: Regular expression: Match Not equal to the string "login"

//Match Not Equal to the string "login"
^(?!login$).+$

How to Delete an element from an array?

In this post, we will answer the question : How to Delete an element from an array?

First of all , we  will create our own array called :$aFruits

  
   $aFruits = array('apple','lemon','grapes','pineapple');
 

Secondly,  if we want to delete the lemon element, we have to use the function called unset and we need to access to  that element by  its  position number.

  
  unset($aFruits[1]);
 

Ouput:
 Array ( [0] => apple [2] => grapes [3] => pineapple )

Mysql SQL Error 1093 You can't specify target table

In this post, we will learn how to resolve this "Mysql Error 1093 You can't specify target table"



I was trying to delete some data using  this query:

DELETE  FROM articles
where art_id  in (select a.art_id
                          from articles a
                         where a.art_date <= '2015-05-19'

                        );
 

When I executed this query an error suddenly appeared that was: Mysql Error 1093 you can't specify target table.


What was the problem?
 Basically, the delete statement doesn’t allow to perform a sub-query using the same table.

How can I overcome this?

The solution, that I found was quite easy, is as simple as this: you have to wrap the sub-query in one more select .

Solution:

DELETE FROM articles
 WHERE art_id in (
     SELECT aid FROM(
      SELECT a.art_id FROM articles a WHERE a.art_date <= '2015-05-19'
  ) as a
 );