TAGS:

ruby  rails  migration  database  add 

Related:

• Creating migration file using generate migration
• Creation migration file using generate model.
• Creating migration file using scaffold.
• Drop tables using migration.
• Editing migration file manually.</li>
• Seeding data into tables via migration.
• Joining two tables via migration.
• Migration specific VERSION or STEP.
• Removing fields from tables via migration.
• Setting rails environment via migration command.
• Setup, reset and drop database
</ul>


Adding Column Or More To An Existed Table.

The general form of `adding` field to table is:

rails g migration AddColumnnameToTablename columnname:datatype

Example, Adding `price` column to `books` table: Then, `Columnname = Price` and `Tablename = Books` and `datatype = float`

rails g migration AddPriceToBooks price:float

Then,

rake db:migrate

If you need to add `many` columns to table you can use:

rails g migration AddDetailsToBooks pages:integer year:integer

Then,

rake db:migrate

Note that you can undo this migration back step by step using:

rake db:rollback

This will delete the `price` column from the `books` table in the database itself. Note, Any `rake db:rollback` may delete stored data in the `targeted` columns and can't be restored again. Also, You can delete the migration file generated by converting `g`(for generate) to `d` (for destroy) in migration command as:

rails g AddPriceToBooks price:float
#to be
rails d AddPriceToBooks price:float

The last line will delete the migration file generted by the first line. Take a look to this tutorial video: