Adding HTML tag in Rails link_to

Recently ,I've been working on Ruby on Rails and  had to do something  like the example shown below, but using the helper link_to:

Example:

    
 
<a data-method="delete"rel="nofollow" href='sign_out'>
<i class="fa fa-sign-out fa-fw"</i>Logout
</a>

After researching, I found the answer, you should add  your html to the link_to helper as shown below:

ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint

If you have ever had this error, is because you want to truncate a table that has foreign key in another table. Let me put it this way.

Having this  structure, where "articles" can have multiple users , and you want to delete the table users using the function TRUNCATE, Mysql will throw this error: ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint

There is a way to avoid this error, but you have to understand,  if you want to delete the  users tables and reset the auto increment field , you have to do the same with the articles table.

This is a basic example, but what would happen if you want to clean an entire database and reset the auto increment? That would be very complicated without the following code.


I know this code could be useful for you:



SYNTAX:

   

     SET foreign_key_checks = 0;

       TRUNCATE  `users`;


       TRUNCATE  `articles`;


     SET foreign_key_checks = 1;

 

Doing that, you will temporarily disabling  referential constraint, and at the end you will enable the referential constraint.

How to Reset auto increment after deleting a table row

To delete data and reset the auto increment field using MYSQL, we have a function called TRUNCATE which will help you to accomplish this task.


Syntax:

   

     TRUNCATE  `articles`;

 

Basically , After the function "TRUNCATE" you have to write your table name , in this case is the table called " ARTICLES" .When you run this SQL sentence you will delete the whole data and the auto increment field will be reset.

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.