In the above diagram, moving left to right
depicts the relationship between organization, location, department & employees in that order respectively. From this
diagram we can say that Organization is at a higher grain than the location, department & employees. The location is at
a higher grain than that of the department & employees. The department is at a higher grain than that of the employees.
Hence, if want a DW for tracking employee related data comprising of all the organization, location & department then
our DW is said to be at the lowest grain. The more lower the grain is, more is the data volume. But more is the information.
There will always be a trade off between data volume & granularity. As we move towards higher grain the data gets to be
more summarized. How is that? Consider we are storing expenses incurred by each employee in a database. Now while considering
the expenses incurred by each department it would be the summation of expenses of each employee. The same can be said with
respect to other higher grains.
Identifying the grain of a warehouse is very important. If a proper grain is not defined then the DW is bound to fail
sometime down the line.
Attitude,Not Aptitude, Determines Altitude