What is the difference between a data warehouse and a data mart?

 In terms of design data warehouse and data mart are almost the same.

In general a Data Warehouse is used on an enterprise level and a Data Marts is used on a business division/department level.

A data mart only contains data specific to a particular subject areas.  

1.1.                     Difference between data mart and data warehouse

Data Mart	Data Warehouse
Data mart is usually sponsored at the department level and developed with a specific issue or subject in mind, a data mart is a data warehouse with a focused objective.	Data warehouse is a “Subject-Oriented, Integrated, Time-Variant, Nonvolatile collection of data in support of decision making”.
A data mart is used on a business division/ department level.	A data warehouse is used on an enterprise level
A Data Mart is a subset of data from a Data Warehouse. Data Marts are built for specific user groups.	A Data Warehouse is simply an integrated consolidation of data from a variety of sources that is specially designed to support strategic and tactical decision making.
By providing decision makers with only a subset of data from the Data Warehouse, Privacy, Performance and Clarity Objectives can be attained.	The main objective of Data Warehouse is to provide an integrated environment and coherent picture of the business at a point in time.