A database refactoring is a small change to your database schema which improves its design without changing its semantics. There are several categories of database refactorings:

• Structural. A change to the table structure of your database schema.
• Referential integrity. A change which ensures that a referenced row exists within another table and/or that ensures that a row which is no longer needed is removed appropriately.
• Architectural. A change which improves the overall manner in which external programs interact with a database.
• Method. A change which improves the quality of a stored procedure, stored function, or trigger.
• Non-refactoring transformations. A change which changes the semantics of your database schema by adding new elements to it or by modifying existing elements.

Category	Database Refactorings
Structural Refactorings	Drop Column Drop Table Drop View Introduce Calculated Column Introduce Surrogate Key Merge Columns Merge Tables Move Column Rename Column Rename Table Rename View Replace LOB With Table Replace Column Replace One-to-Many With Associative Table Replace Surrogate Key with Natural Key Split Column Split Table
Referential Integrity Refactorings	Add Foreign Key Constraint Add Trigger for Calculated Column Drop Foreign Key Constraint Introduce Cascading Delete Introduce Hard Delete Introduce Soft Delete Introduce Trigger for History
Architectural Refactorings	Add CRUD Methods Add Mirror Table Add Read Method Encapsulate Table With View Introduce Calculation Method Introduce Index Introduce Read Only Table Migrate Method From Database Migrate Method to Database Replace Method(s) With View Replace View With Method(s) Use Official Data Source
Method Refactorings	Add Parameter Consolidate Conditional Expression Decompose Conditional Extract Method Introduce Variable Parameterize Methods Remove Control Flag Remove Middleman Remove Parameter Rename Method Reorder Parameters Replace Literal With Table Lookup Replace Nested Expression With Guard Clauses Replace Parameter With Specific Methods Split Temporary Variable Substitute Algorithm
Non-Refactoring Transformations	Insert Data Introduce New Column Introduce New Table Introduce View Update Data