star schema: it is a highy de-normilised techinque... in this one fact table is associated with n number of dimensions table... .. it looks like a star.. snow Flake Schema: If We apply normilised Princples to Star Schema Then It is Known As Snow Flake Schema.. In This Each Demsion Table Associated With Sub Dimenson Table..
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RE: what is the difference between star schema and sno...
Star Schema : Star Schema is a relational database schema for representing multimensional data. It is the simplest form of data warehouse schema that contains one or more dimensions and fact tables. It is called a star schema because the entity-relationship diagram between dimensions and fact tables resembles a star where one fact table is connected to multiple dimensions. The center of the star schema consists of a large fact table and it points towards the dimension tables. The advantage of star schema are slicing down performance increase and easy understanding of data.
Snowflake Schema : A snowflake schema is a term that describes a star schema structure normalized through the use of outrigger tables. i.e dimension table hierachies are broken into simpler tables.
In a star schema every dimension will have a primary key.
In a star schema a dimension table will not have any parent table.
Whereas in a snow flake schema a dimension table will have one or more parent tables.
Hierarchies for the dimensions are stored in the dimensional table itself in star schema.
Whereas hierachies are broken into separate tables in snow flake schema. These hierachies helps to drill down the data from topmost hierachies to the lowermost hierarchies.
RE: what is the difference between star schema and sno...
Both these schemas are generally used in Datawarehousing.
Star schema as the name indicates resembles the form of star as there is only one fact table which is associated with numerous dimension tables (with the help of foreign keys).This schema depicts a high level of denormalized view of data.
However in Snowflake schema the dimension tables are further normalized into different tables (fact table is single in this schema also).This schema stores data in a more normalized form .
It depends on scenario as how much data is generally there in the datawarehouse generally star schema is preferred.
RE: what is the difference between star schema and sno...
star schema: it is a highy de-normilised techinque... in this one fact table is associated with n number of dimensions table... .. it looks like a star.. snow Flake Schema: If We apply normilised Princples to Star Schema Then It is Known As Snow Flake Schema.. In This Each Demsion Table Associated With Sub Dimenson Table..
RE: what is the difference between star schema and snow flake schema ?and when we use those schema's?
Star Schema means A centralized fact table and surrounded by different dimensions Snowflake means In the same star schema dimensions split into another dimensions
Star Schema contains Highly Denormalized Data
Snow flake contains Partially normalized data
Star cannot have parent table But snow flake contain parent tables. Need to go for Star: Here
Simply database
Support drilling up options
Need for Snowflake schema: Here some times we used to provide? seperate dimensions from existing dimensions that time we will go to snowflake
Dis Advantage Of snowflake: Query performance is very low because more joiners are present
RE: what is the difference between star schema and snow flake schema ?and when we use those schema's?
Star Schema: Definition: The star schema is the simplest data warehouse schema. It is called a star schema because the diagram resembles a star with points radiating from a center.
A single Fact table (center of the star) surrounded by multiple dimensional tables(the points of the star). Advantages:
Simplest DW schema
Easy to understand
Easy to Navigate between the tables due to less number of joins.
Most suitable for Query processing Disadvantages:
Occupies more space
Highly Denormalized
Snowflake schema:
Definition: A Snowflake schema is a Data warehouse Schema which consists of a single Fact table and multiple dimensional tables. These Dimensional tables are normalized.A variant of the star schema where each dimension can have its own dimensions.
Advantages:
These tables are easier to maintain Saves the storage space.
Disadvantages:
Due to large number of joins it is complex to navigate
Starflake schema - Hybrid structure that contains a mixture of (denormalized) STAR and (normalized) SNOWFLAKE schemas.
RE: what is the difference between star schema and snow flake schema ?and when we use those schema's?
1. Star shema is Demormalised data but in snowflack schema its normalised 2. when when star schema splited into it become to snowflack schema 3. Performace will be more on star schema but performance less in snoflack schema due to joins 4. Star schema is simple but snowflack is complex 5. Dimention table in star schema having no maste table but Dimention table in snowflack having so many maste table. 6. Star schema having one fact table sarounded by dimetion table but incase of snowflack schema more than one fact table sarrounded by dimetion table.
RE: what is the difference between star schema and snow flake schema ?and when we use those schema's?
Accurate information is star schemas have more joins because it has only one dimension table per fact and so to retrieve more queries we have to use joins...
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