I am very new the vertica . Can somebody tell me, how to use projection ? Also at what time we shoul

Please follow the link what Amelia sent you to know in detail, in a nutshell -

Projections are the storage of data of tables for each table, there should be at least one projection (called super projection) for each table you create and may have also other projections based on the requirements but those are duplication of full/part data for some purpose.

These are created automatically when you load the data in the table ( by insert/COPY) although before loading you can create them manually using certain syntax. Also they are created if you use DBD in admintools.

Thanks for sharing the link.. It has more details in it. For any clarification i will revert back to you.

Thank you Prasanta for answering.
That means in normal other SQL table all the data will store in Table level , but in vertica it stores in Projects level( this is the major difference).
So one clarification i need , that means it will not create projection when we will just create table ??

#Soumya.

A single projection is automatically created when the first row of a table is inserted. This projection is called super projection
So lets say you create table A, at this point there is no projection for Table A.
When you insert your first record into Table A, at this point of time a Super projection will be created for table A automatically.

This was about Super projections.
You can also design and create projection manually with a simple SQL CREATE PROJECTION statement.

For more info on Projections in Vertica, you can refer this link

http://vertica-forums.com/viewtopic.php?f=6&t=977&p=3023&hilit=projections#p3023

Hope this helps.

Thanks Navin. I am clear now.