  With the development of decision systems and specially data warehouses, the
visibility of the data warehouse design before its creation has become
essential, and that because of data warehouse importance as considered as the
unique data source giving meaning to the decision. In a decision system the
proper functioning of a data warehouse resides in the smooth running of the
middleware tools ETC step one hand, and the restitution step through the data
mining, reporting solutions, dashboards... etc other. The large volume of data
that passes through these stages require an optimal design for a highly
efficient decision system, without disregarding the choice of technologies that
are introduced for the data warehouse implementation such as: database
management system, the type of server operating systems, physical server
architecture (64-bit, for example) that can be a benefit performance of this
system. The designer of the data warehouse should consider the effectiveness of
data query, this depends on the selection of relevant indexes and their
combination with the materialized views, note that the index selection is a
NPcomplete problem, because the number of indexes is exponential in the total
number of attributes in the database, So, it is necessary to provide, while the
data warehouse design, the suitable type of index for this data warehouse. This
paper presents a comparative study between the index B-tree type and type
Bitmap, their advantages and disadvantages, with a real experiment showing that
its index of type Bitmap more advantageous than the index B-tree type.
