Column types and attributes in Ruby on Rails

Introduction

Columns store data in a database table. Different types hold different kinds of information.

When creating a new database table to store user information.

When adding a new feature that needs to save dates or numbers.

When defining what kind of data each column should hold to keep data organized.

When setting rules like making sure a column cannot be empty.

When optimizing storage by choosing the right data type for each column.

Syntax

Ruby on Rails

create_table :table_name do |t|
  t.column_type :column_name, options
end

Replace column_type with the type like string, integer, or boolean.

Options can include null: false to require a value or default: value to set a starting value.

Examples

This creates a text column for short strings.

Ruby on Rails

t.string :name
# Stores text data like names or titles

This column must have a number and starts with 0 if no value is given.

Ruby on Rails

t.integer :age, null: false, default: 0
# Stores whole numbers, cannot be empty, starts at 0

Good for flags like if a user is active or not.

Ruby on Rails

t.boolean :active, default: true
# Stores true or false values, defaults to true

Used to track when something was created or updated.

Ruby on Rails

t.datetime :created_at
# Stores date and time information

Sample Program

This migration creates a users table with columns for username, age, admin status, and join date. It also adds timestamps for created_at and updated_at automatically.

Ruby on Rails

class CreateUsers < ActiveRecord::Migration[7.0]
  def change
    create_table :users do |t|
      t.string :username, null: false
      t.integer :age, default: 18
      t.boolean :admin, default: false
      t.datetime :joined_at

      t.timestamps
    end
  end
end

Important Notes

Always pick the smallest column type that fits your data to save space.

Use null: false to make sure important data is always there.

Default values help avoid errors when no data is given.

Summary

Columns define what kind of data a table holds.

Choose types like string, integer, boolean, or datetime based on your data.

Use attributes like null and default to control data rules.