difference between context and alias

[ksk2]

Hi,
can any one please tell me the exact difference between context and alias .
b'coz iam not sure of alias so all this days i was working only on context.. b'coz recently I came to know with some one that alias will also works as context.
is that right?

note: if possible please reply with one example.. in both alias and context

Thanks for help in advance..
ksk2

 

[RogerCruse]

Get this book - Business Objects Companion by David Jackson.

It will give you enough information to understand the differences.

Or check your original Business Objects training material.

 

[PAULSGS]

A context is required if you have more than one route to a table, this would be because you can join to it from more than one table.

If you really do need the table to be joined twice, from different routes, you can create a copy of the table - an alias - and re-route one of the joins to this. Doing this eliminates the need for contexts.

This copy, or alias exists at the BO level and doesn't physically create a copy on your database, it serves to modify the sql that is generated

 

[ksk2]

Thanks PAULSGS

 

[sagars]

IS use of Alias a good idea or COntext?

 

[blom0344]

Hello sagars,

Designer's manual (PAGE 144 onwards) gives some idea when to use context or alias. From a designer's point of view using a context is a much more sophisticated way to solve ambiguous query paths, cause you force a query to stay within the right 'tracks'. However, the end-user creating a report is confronted with the database-structure if he is asked to choose between contexts. The whole idea of universes in BO is to avoid such a confrontation!!
When you use an alias, the end-user will not have this confrontation, but somehow it has to be obvious that he has to choose object relating to the alias. You can steer him in the right direction by carefully setting up classes, subclasses and objects.

So , if you only use reports that are created by superusers who know their business , using contexts is not a problem, but if anyone can create their own reports it´s another story! T. Blom
Information analist
Shimano Europe
tbl@shimano-eu.com

 

[sagars]

Hi T Blom!

Thanks for this info, but dont you think creating alias will have performance issues? Becuase, if I create a alias means I duplicate the table. therefore:
1) More Memory
2) The alias created will not be indexed, therefore a search on it will definitely be slow.

Further more, Designer doesnt allow me to create a Alias always (depending on the number of lookup(root) tables and fact table).

Correct me if I am carrying some wrong infor with me.


Thanks,

Sagar

 

[blom0344]

Hello Sagar,

First part of your question:

Yes , your are wrong. Creating an alias has nothing to do with creating a new table. The universe is not the actual database but a description of relations between tables in the database. An alias just reroutes the SQL carried out.
Forget indexes and stuff like that, data comes from one database table only.
Do yourselve a favour and spend some time with the designers manual, there is quite a bit about when to use an alias / context.
T. Blom
Information analist
Shimano Europe
tbl@shimano-eu.com