1. Usage & Type
   1. OLTP
   2. OLAP
2. Distribution Model
   1. Software
      1. SQL Server
      2. Teradata
      3. Oracle
   2. Appliance
      1. SAP HANA
      2. Netezza
      3. Oracle Exadata
   3. Online
      1. APEX
3. Design
   1. Relational
      1. Normalized
         1. 3NF
         2. 2NF
         3. 1NF
      2. Denormalized
   2. Flat structure
4. Storage mechanism
   1. Row based
   2. Column based
   3. In Memory
5. Properties
   1. Atomic
   2. Consistent
   3. Isolated
   4. Durable
6. Scale
   1. Personal
   2. Enterprise