3 tier - What is the difference between Database Abstraction Layer & Data Access Layer?

Question

I am actually stuck in 3-tier structure. I surfed the internet and found two terminologies "Database Abstraction Layer" & "Data Access Layer".

What are the differences between the two?

Answer 1

Data Access Layer= Create, Read, Update, Delete (CRUD) operations specific to your application domain

Data Abstraction Layer= performs generic database operations like connections, commands, parameters insulating you from vendor specific data libraries and providing one high level api for accessing data regardless of whether you use MySQL, Microsoft SQL Server, Oracle, DB2, etc...