SharePoint is not meant to replace database, SharePoint is evolving as a "Enterprise Content Management and Collabration" Software or Application Development Platform depending on the target audience.
SharePoint List doesn't support
1) Relationship (other then simple relationships)
2) Transactions
SharePoint List supports
1) Indexing
2) Sorting
3) Filtering
4) Views
There are some third party tools (like SLAM), which helps in making relationships between lists. But keep in mind they have limitations and performance issues as SharePoint is not a RDBMS. We can't fly a passenger plane to moon, you need a rocket.
