Rails generate migration main commands create, delete, update.

1. Active Record Migration are commands that allowed to create tables and update the schema.rb file. Schema is the file that holds all the data base.

$ rails g migration [tableNames]

This command creates table. In db folder is generated a new table and it looks like this…

Here can be made any changes needed, add more columns or fix syntax errors etc. Afterwords is necessary to run rake db:migrate to update the schema and push the data to databases.

$ rake db:migrate

2. If is needed to add a column to an existing table, follow the next steps

$ rails g migration addColumnToExistingTable

This command will create a table in db folder. Below is represented the format and order on how we add a column to an existing table.

:onePage — is the table name

:email — is the column name

:string — is the format

Here it can be added multiple columns for example

After any change, save the file and run again …

$ rake db:migrate

3. In case is needed to delete a table , run the next command

$ rails g migration drop_tablename

This command deletes a table from DB and updates the schema.

4. In case we want to change the name of created table, here is the solution

$ rails g migration change[OldTableName]To[NewTableName]

Created file…

As mentioned before after saving the file is necessary to run…

$ rake db:migrate

This are main commands to create update and delete a table in Active Record Migration.

Scaffold is an other way to build tables along with controllers, models and view files.

Happy Coding!

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