do we have to always use SUM or some aggregate functon in ‘select’ of the Object when I create a measure though the aggregate projection is defined as SUM or somethinhg?
I am also able to do SUMs and Counts on Dimension Objects. Then why should I create Measure Objects. Why can’ I just create some variables at Web-I instead of measure objects. I am confused with Measures and Dimension objects.
BOBJGuy 
(BOB member since 2010-02-25)
If you have 3 million rows and don’t use sum in the measure declaration, then you’ll return all 3 million rows in the report and be really popular with your server admins.
You wouldn’t write it that way in SQL, so why write it that way in Business Objects?
Short answer: yes. The reason is that an aggregate function in the select definition of a measure and projection function serve different purposes. The purposes have been mentioned and discussed on BOB many times before. Please use search to find those topics.
Marek Chladny 
(BOB member since 2003-11-27)
I posted a blog post summarizing why you need both an aggregate and a projection function on your measures.
SQL Aggregate Versus Universe Projection
I wrote the post because - as observed - this question comes up frequently. Now I don’t have to rewrite the answer, I can just link…
Dave Rathbun 
(BOB member since 2002-06-06)
Thank you All.
BOBJGuy (BOB member since 2010-02-25)
See also this post on Aggregation vs. Projection for measures, please.
Andreas 
(BOB member since 2002-06-20)