Database refactoring

1. To develop the schema in an evolutionary manner in parallel with the evolutionary design of the rest of your system.
2. To fix design problems with an existing legacy database schema. Database refactorings are often motivated by the desire for database normalization of an existing production database, typically to "clean up" the design of the database.
3. To implement what would be a large change as a series of small, low-risk changes.

   Database refactorings

• Splitting an aggregate table into two different tables in the process of.
• Renaming an existing column to make its purpose clearer.
• Combining two columns into a single one because they were being used for the same purpose.
• Splitting an existing column into two or more columns because the original column was being used for several purposes.
• Applying a common data format to a column so as to increase the consistency of the data.
• Common code refactorings to database code such as stored procedures and triggers.
• Introducing a view to implement a common access path to data.

  Process of database refactoring

1. How to implement a single refactoring
2. How to track/share database refactorings across your organization
3. How to apply a series of database refactorings to a database