Snow Flake Schema

anybody give me some knowledge about snow flake schema.
in which type of situations,useually snow flake schema creates in data model.
can you please provide me with example?
Thanks in Advance.

In case of large dimesnsion, we will split them to smaller dimensions, this is to make the table better manageable.
Let's take an example you have a Dimension table which stores the information about the shop details, you may have a seperate dimension table which hold the dempgraphic information of the sales area this provide the logical separation of data.
You have to decide based on your data and requirement whether to go for snowflake or Star.
If you have snowflake defined, will be flattened the same in the logical layer of OBIEE.
Thanks,
Vino

Similar Messages

Question for integration star and snow flake schema in data warehouse

Dear Reader,
I facing a problem like that
I have two data warehouse, one use star schema, other use snow flake schema. I would like to integrate both of them into one data warehouse. What is the strategy should these two data warehouse adopt in order to integrate int one data warehouse?
Should I scrap both data warehouse and build a new one instead, or scrap one of them and use the other?
What factors should be considered in order for me to more easily resolve the differences between the two data warehouses.
Please advise. Thank you very much.

Hi Mallis,
This is a very broad question and the answer depends on so many factors. Please go through the following articles to get an
understanding of what the differences are when to use which.
When do you use a star schema and when to use a snowflake schema -
http://www.information-management.com/news/10000243-1.html
Star vs Snowflake Schemas – what’s your belief? –
http://www.networkworld.com/community/blog/star-vs-snowflake-schemas-%E2%80%93-what%E2%80%99s-your-belie
Hope this helps!

Reg Snow Flake schema design

Hi Experts,
Can any one post few scenarios regarding Implementation of snow flake schema which can not be converted to star schema in BMM layer for better under standing about schemas. I searched my blogs but i did not found exact answer.
Regards,
Rafi

Rafi,
Check these links
http://iniu.net/content/obiee-define-star-schema-over-snowflake-data-model-data-source
http://www.varanasisaichand.com/2012/05/denormalizing-physical-tables-in-bmm.html
http://majendi.blogspot.com/2009/01/obiee-snowflakes-and-stars-part-3.html
http://blogs.datadirect.com/2012/02/obiee-oracle-business-intelligence-integration-with-salesforce-com-crm-and-database-com-via-odbc.html
In general if you follow the OBI best practices you never get snowflake schema in BMM layer.
If helps pls mark

Star schema and snow flake schema

can any one tell star schema is better or snow flake schema is better why
thx in advance

Hi,
Difference : http://www.diffen.com/difference/Snowflake_Schema_vs_Star_Schema
When it comes to OBIEE star schema will be easy to configure because it don't involve much tables where as snow flake schema need to denormalize the tables in BMM layer to get the desired model but again it all depends on how your system was designed
HR schema which is more like a snow-flake schema structure
Refer http://www.varanasisaichand.com/2012/05/denormalizing-physical-tables-in-bmm.html
Thanks,
Saichand

Multiple star or snow flake schema for universe

Hi,
I would like to know following things
1. Can we use more than one star or snow flake schema for an universe? and how to do this?
2. Using multiple shemas for one universe is it good practice or not?
Regards,
Manjunath

Manjunath,
This is exactly where BusinessObjects excels.
When dealing with multiple fact tables, you use contexts.
Contexts are very simple to understand and you must take your time to do so if you are going to successfully develop universes based on more than one fact table. No matter what universe you build, the rule for contexts is always the same; there are no different circumstances based on, say, industry.
Each context starts with a base table, typically a fact table, where all its joins are at the many end of the relationship. The joins are then followed out through the joined tables up other joins where they in turn are at the many end, as in a snowflake schema.
For example, consider the very basic schema below:
D1 -< D2 -< F1 >- D3 -< F2 >- D4
There are two tables that only have many joins attached to them - F1 and F2.
Starting with F1, I can move to D2. I can also move from there to D1. In the other direction, I can move from F1 to D3. However, I cannot move from D3 to F2 because the join cardinalities are in the wrong direction. So, I've found all the joins that belong in the first context. They are D1-D2, D2-F1 and F1-D3. By the same process, I will get to the second context containing joins D3-F2 and F2-D4.
It doesn't work well with many-to-many joins, but you really shouldn't be facing these in a well-designed multi-star.
As for one-to-one joins, set the cardinality as one-to-many in the direction that you know the relationship should be in for the ownership to work out correctly..
The process that I've described above is essentially how the Detect Contexts algorithm works.
The only remaining thing for you to read up on is the SQL parameters but essentially you need ot be able to select multiple contexts and generate multiple sql statements for each context. Otherwise, what's the point in defining them?!!
Hope that clears it up for you.
Regards,
Mark

Snow flake schema to star schema

Hi Gurus,
I am having a snow flake schema how can i turn it into star schema.
thanks,
kumar

In Obiee You can use multiple table source and join 2 tables abd make as singel table.
EX A->B->C
Now we need to join B,C and call it D. Then A->D is star Schema.
Steps is. Join B and C in the physical layer. join B to A Drop B into the Logical layer, Now Drop C on top od the B.
Table B wil get all the column from C. Here it wont create 2 sources, It will look like single source only.
IN the column mapping you can mpa the column to desired physical table.
Later as usula you can join B and A in logical layer.
Get A and B into presentaion layer.
mak if correct/helpful
fiaz

How to make snow flake schema to star in Business layer

i have snow flake data model.
anybody tell me how can i convert that snow flake to star by doing the adding multiple sources to a dimention.
how to do the joins with 2 dimention tables in the business layer

Hi
we can do that for example we have dimension table that connected with another dimension table in physical layer
solution- create one new dimension table in bmm layer and drag the columns from two dimension table which in physical layer and give the join condition it ll work,...
Regards
prabhu haridass

URGENT MODELING SNOW FLAKE SCHEMA

Hi i have 2 fact tables fact1 and fact 2 and four dimension tables D1,D2,D3 ,D4 & D1.1 ,D1.2 the relations in the data model is like this :
NOTE: D1.1 and D1.2 are derived from D1
[( D1.. 1:M..> Fact 1 , D1.. 1:M..> Fact 2 ), (D2.. 1:M..> Fact 1 , D2.. 1:M..> Fact 2 ), ( D3.. 1: M.> Fact 1 , D3.. 1:M..> Fact 2 ),( D4.. 1:M..> Fact 1 , D4 ... 1:M..> Fact 2 )]
Now from D1 there is a child level like this: [D1 --(1:M)..> D1.1 and from D1.1.. 1:M..> D1.2.. 1:M..> D4]
Please help me how to design in physical layer and BMM layer. I will be very glad to you guys this is very urgent requirement.
PS: Deepak Gupta you are very helpful earlier please help me.
Thanks,
ch

They too are snowflake.... but we speak snowflake w.r.t dimension attached to FACT...
Alternate solution, but of the same type..
First of all create aliases for all the Tables in physical layer... but create two aliases for D1 , say D1.A1 & D1.A2
Note: you need to create joins between aliases only, no need of creating joins between original tables ..
In Physical Layer, just have all the joins as Physical Foreign Key Join, just the way you have described, making sure that
D1.A1 is connected only to both the facts aliases...
and
D1.A2 is connected only to D1.1 alias
Drag all the aliases in BMM
Now work with Aliases only in BMM Layer
Here D4 is snowflaked...
So in BMM just bring D4 Alias from Physical Layer and onto it, drop D1.1 alias, D1.2 alias and D1.A2 alias , so that now you have 4 logical table sources under 'Logical Table folder' D4.
This is it....
The Only thing is that you ll have to create two Aliases for D1...
Thanks
Ashish Gupta

Snow flake problem

Hello
whats the procedure to resolve the problem if we are able to only build a snowflake schema
my tables are like this:
fact table: sales
dimesion tables: customers, products, orders
other tables that are connected to dimension tables with primary keys are "countries" is connected to "customers" and orders_inventory is connected to orders
so it is forming a snow flake in physical layer and how to we do make in BMM to form a star schema
if we are dragging columns from countries to customers in BMM, will that work effiecently as expected because as a user i am not able to see the data from both the tables. i am working on SH schema from ORACLE 10g database
thanks
rake

rake,
I suggest you do some reading on dimensional modeling and use aliases and multi-source LTSs
You'd need to model in such a way as to avoid circular joins.

Best practice for making a report of 10,000 to 20,000 rows(OBIEE 10.3.4.1)

My Scenario is like this:*
Hi i have 2 fact tables fact1 and fact 2 and four dimension tables D1,D2,D3 ,D4 & D1.1 ,D1.2 the relations in the data model is like this :
NOTE: D1.1 and D1.2 are derived from D1 So D1 might be snow Flake.
[( D1.. 1:M..> Fact 1 , D1.. 1:M..> Fact 2 ), (D2.. 1:M..> Fact 1 , D2.. 1:M..> Fact 2 ), ( D3.. 1: M.> Fact 1 , D3.. 1:M..> Fact 2 ),( D4.. 1:M..> Fact 1 , D4 ... 1:M..> Fact 2 )]
Now from D1 there is a child level like this: [D1 --(1:M)..> D1.1 and from D1.1.. 1:M..> D1.2.. 1:M..> D4]
Please help me in modeling these for making a report of 10,000 rows and also let me know for which tables do i need to enable cache?
PS: There shouldn't be performance issue so please help me in modeling this.
Thanks in Advance for the Experts who are helping me for a while.

Shudn't be much problem with just these many rows...
Model something like this only Re: URGENT MODELING SNOW FLAKE SCHEMA
There are various ways of handling performance issues if any in OBIEE.
Go for caching strategy for complete warehouse. Make sure to purge it after every data load..If you have aggr calculations at higher level then you can also go for aggregated tables in OBIEE for better performance.
http://www.rittmanmead.com/2007/10/using-the-obiee-aggregate-persistence-wizard/
Hope this is clear...Go ahead with actual implementation and lets us know incase you encounter any major issues.
Cheers

Support date range and as of date in Universe

Hi,
I have some questions on Universe design best practices. Can you please help ?
We are using BO4 SP7 and UDT for universe design.
Little bit on our schema: snow flake schema with multiple fact tables. Most of our table are 'Pure Type 6' dimension tables in which start date and end date are used to track historical data. We also have date dimension table. We want to support both 'As of date' and custom 'date range' type reporting.
Out typical use cases are like
1. All items As of date
2. All items between dates etc.
How can we model it in the Universe ?
1. We can not join every dimension with date_d dimension. So we have decided to put default conditions at Folder level. Our typical date conditions as below.
date_d.end_full_date_utc between diminetion1_d.start_date AND diminetion1_d.end_date
But problem is, table condition are not always applied. If we have A, B and C folders and if I create report by using objects from A and C then non of the condition applied to B appears in the query. This is problem for us.
2. Other approach we thought is to define start and end prompt and define a restriction condition for each and every table.
diminetion1_d.start_date > [start_date_prompt] AND diminetion1_d.end_date < [end_date_prompt]
We thought it will be too munch work as we have more than 150 tables and also 2 prompts will always appear, even of as of date, which may not look good.
3. Is there a way apply to apply these date conditions at the individual table level so that they will appear in Query when ever the table is involved in the join path ?
3. What is the best way to handle this kind of requirements, please suggest ?
Thanks

Hi,
I have some questions on Universe design best practices. Can you please help ?
We are using BO4 SP7 and UDT for universe design.
Little bit on our schema: snow flake schema with multiple fact tables. Most of our table are 'Pure Type 6' dimension tables in which start date and end date are used to track historical data. We also have date dimension table. We want to support both 'As of date' and custom 'date range' type reporting.
Out typical use cases are like
1. All items As of date
2. All items between dates etc.
How can we model it in the Universe ?
1. We can not join every dimension with date_d dimension. So we have decided to put default conditions at Folder level. Our typical date conditions as below.
date_d.end_full_date_utc between diminetion1_d.start_date AND diminetion1_d.end_date
But problem is, table condition are not always applied. If we have A, B and C folders and if I create report by using objects from A and C then non of the condition applied to B appears in the query. This is problem for us.
2. Other approach we thought is to define start and end prompt and define a restriction condition for each and every table.
diminetion1_d.start_date > [start_date_prompt] AND diminetion1_d.end_date < [end_date_prompt]
We thought it will be too munch work as we have more than 150 tables and also 2 prompts will always appear, even of as of date, which may not look good.
3. Is there a way apply to apply these date conditions at the individual table level so that they will appear in Query when ever the table is involved in the join path ?
3. What is the best way to handle this kind of requirements, please suggest ?
Thanks

How to retrieve data from a dimension that is not directly joined to a fact

Hi,
In my case I have 2 dimensions and one fact. I need to runa report collecting data from all the three tables.
I need to do the following.
DIMA DIMB FACT1
FACT1 is joined with DIMA
DIMA is joined with DIMB
FACT1 is not Joined with DIMB.
My report should still retrieve information from DIMB by connecting FACT1 with DIMA and retrieve corresponding data from DIMB.
Please suggest how can I do this .
I am using 10.1.3 version of OBIEE
You help will be much appreciated.

Hi,
I think your data model is snow-flake schema,we can get the data from snow-flake schema also.Pull the columns from both fact and DIMB into criteria.It will display the result.
mark if helpful/correct...
thanks,
prassu

How to build the best Purchasing Propensity Model

Hello, I'm trying to develop a Market Basket Analysis using over 90 different categories and I'm not quite sure which model would be the best option for this amount of variables?
Also I could use some direction on which algorithms and variables are the most relevant in the construction of a Purchasing Propensity Model (e.g. age, frequency of purchase, average ticket value, purchases in other categories, etc.)
Thanks in advance for your help

hi user,
Few things u should keep in mind
1) Take the tables and find the relation ship between those(pk-fk)
2) Identify Dim's and Fact's
3) After step2 definitely there will be a division of header level and detail tables
4) Dim1 having Business_Date and Fact1 having Business_date u can join in this way
5) Normally without ETL we may go for Pl/SQL or SQL's.Your Data model will come under this point
6)In BMM layer u can form Start Schema/Snow flake schema
Thanks,
Saichand.v

How to backup music from a 3G that is not in service to itunes

how do you backup music to itunes from a 3G that is not in service ?

Hi,
I think your data model is snow-flake schema,we can get the data from snow-flake schema also.Pull the columns from both fact and DIMB into criteria.It will display the result.
mark if helpful/correct...
thanks,
prassu

Fact table enriched with hierachy information

Hi Guys,
I have a fact table design question.
The fact data table (oracle10g) on bottom level RelationshipManager (RM) contains the data columns
for the RM dimension:
FACT TABLE
ID¦RM¦DEPARTMENT¦AGENCY¦REGION¦SALES
1---23--Bronx------------NY---------US-------23232
2---24 ---------------------NY---------US-------87878
3---25-----------------------------------US------ 9999999
This means the fact has been enriched with hierachy information, this is not whats usually done.
Why have I done it? Because the RM is not necessarily always part of a department BUT can also
be directly placed under an agency or a region (agency or region leads).
Have I made the right choice by chosing to enrich the fact table? I could have also build a snow flake
schema by storing hierachy information in a seperate table.
Thanks.

with your problem, it might be best to split the dimension into multiple dimensions or multiple attribute dimensions with default values where you do not have a value for example set up RM with a N0_RM and when you don't have data load it there. If I'm looking at this correctly, the problem it appears you have is you have an inconsistent hierarchy. where the rollups can change. having them in the same dimesion would be problematic. If therewere consistancy then you could add members into a single hierarchy something like
US
--No_State
--NY
-----Bronx
------RM23
------No_RM
but from your example I don't see it. If they are seperate dimensions(not attribute dimensions) then you could load based on date. If they are attribute dimensions, then look at varying attributes

Snow Flake Schema

Similar Messages

Maybe you are looking for