Sithu
Answered On : Oct 4th, 2005
Type-1
Most Recent Value
Type-2(full History)
i) Version Number
ii) Flag
iii) Date
Type-3
Current and one Perivies value
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sai
Answered On : Oct 7th, 2005
fine
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Henry
Answered On : Oct 18th, 2005
SCD
Type 1 : overwrite data is to be there.
Type 2 : current, recent and history data should be there.
Type 3: current and recent data should be there.
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sranjanim
Answered On : Oct 21st, 2005
Henry Wrote:
SCD
Type 1 : overwrite data is to be there.
Type 2 : current, recent and history data should be there.
Type 3: current and recent data should be there.
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ravi kumar guturi
Answered On : Mar 14th, 2006
SCD means If the data in the dimension is happen to change very rarely,
Mainly SCD 3 types
1)SCD-1:HERE THE PREVIOUS DATA OVERWRITE BY CURRENT DATA
MEANS HERE ONLY MAINTAIN CURRENT DATA.
2)SCD-2: HERE JUST ADD THE ADDITIONAL RECORDS
IN SCD2 3 TYPES1)VERSIONING2)FLAGVALUE3)EFFECT DATE RANGE
VERSIONING: MEANS HERE JUST SEND THE UPDATED RECORDS TO THE TARGET ALONG WITH VERSION NUMBER.
NEW RECORDS WILL BE SENDING TO THE TARGET ALONG WITH PRIMARY KEY
FLAGVALUE:HERE UPDATED RECORDS SEND TO THE TARGET ALONG WITH 0
AND RECENT RECORDS SEND TO THE TARGET ALONG WITH 1
EFFECTIVE DATE RANGE:MEANS HERE TRACKS THE BOTH PREVIOUS AND CURRENT DATA
3)SCD-3: HERE MAINTAINS JUST PREVIOUS AND CURRENT DATA.
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Arvind Kumar
Answered On : Jan 29th, 2007
Type1: Rows containing changes to existing dimensions are updated in the target by overwriting the existing dimension. In the Type 1 Dimension mapping, all rows contain current dimension data. Use the Type 1 Dimension mapping to update a slowly changing dimension table when you do not need to keep any previous versions of dimensions in the table. Type 2: The Type 2 Dimension Data mapping inserts both new and changed dimensions into the target. Changes are tracked in the target table by versioning the primary key and creating a version number for each dimension in the table. Use the Type 2 Dimension/Version Data mapping to update a slowly changing dimension table when you want to keep a full history of dimension data in the table. Version numbers and versioned primary keys track the order of changes to each dimension. Type 3: The Type 3 Dimension mapping filters source rows based on user-defined comparisons and inserts only those found to be new dimensions to the target. Rows containing changes to existing dimensions are updated in the target.
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SCD means Slowly Changing Dimension.
The price of the product, address of the person, name of the city are few examples of SCD.
There are three methods to capture SCD.
Type 1: Overwriting the old values
As the old value is overwritten by the new (current) value, there is no way to find out what the old (historical) value(s) were. In other words, it holds ONLY current value.
Type 2: Adding an additional record in the dimension table
In this case, an additional record is added in the dimension table. This method is very useful for the ACCURATE reporting purpose as all the OLD VALUES are captured. In this method, we need to change the table structure so that PK violation doesn't take place. Generally speaking, addition of the columns like "Effective Date" and "Expiary Date" suffice the need.
Type 3: Addition of the column (old value) in the dimension table.
In this method, when the value of the dimension is updated (by the current value), the old value column of the table is updated by the most previous value of the dimension. Thus we have the CURRENT value and the MOST PREVIOUS value of the dimension. This method is also NOT EFFECTIVE when reporting is needed over the period of time when the value of the dimension has changed more than once.
Thanks.
Alpesh
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SCD-1 (Current)
Overwriting the old values in the dimension record.
SCD-2 (History and Current)
Creating an additional dimension record at the time of the change with the new attribute values.
SCD-3 (Previous and Current)
Creating new current fields and move the old attribute in a precedent field.
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