• 4.6 Script the upgrade and downgrade of a database
  • Learning Objectives
  • Use this for subheaders
  • Apply database changes (OPTIONAL)

4.6 Script the upgrade and downgrade of a database

Learning Objectives

By the end of this lesson you will be able to:

• Upgrade and downgrade the database through a script.

Use this for subheaders

1. Create a new target in database-integration.xml as shown below. Modify the database driver.

   <target name="update-database"> <taskdef name="updateDatabase" classname="liquibase.ant.DatabaseUpdateTask" classpathref="project.class.path" /> <updateDatabase changeLogFile="database.changelog.xml" driver="org.apache.derby.jdbc.EmbeddedDriver" url="jdbc:derby:brewery" username="" password="" dropFirst="true" classpathref="project.class.path"/>

2. Create a new file called database.changelog.xml and put it in the software directory.

   “` <?xml version=“1.0” encoding=“UTF-8”?>

   “`

3. Be sure to include the new Ant target as a dependent target. Then, run the Ant build again. Go to MySQL to find the change.

Apply database changes (OPTIONAL)

1. Change to the sample_app directory.

   cd ~/sample_app

2. Rollback changes that were previously applied to a database.

   sudo rake db:rollback

3. The example below is part of the sample application for Ruby on Rails Tutorial: Learn Rails by Example by Michael Hartl. You can also define the database schema in a script.

   “`

   class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.string :name t.string :email

   t.timestamps
   

   end end

   def self.down drop_table :users end end

   “`

4. The example below is using a tool called Liquibase for database change management.

   “`

   “`