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Please explain me the difference between 3 types of slowly
changing dimension in datawarehousing?
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Answer / rameshgoud
scd1-> with this process we can maintain only updated data,
for ex- if a record inserted in source then the same record
should be inserted in targer, if a record updated in the
source then same update should process in target, so here
we cant maintain the history
scd2->with this we can maintain current data and complete
historical data by adding the start_date and end_date of
the records in the target table. If a records get updated
in the source same record will insert in the target as new
record and the old record is updated with end date as
todays date. Like wise we there will no be any deletion of
records, so we can maintain the compelte history here.
scd3-> using this we can maintain current and recent
historical data only
for every source possible changing column we need two
target columns as NEW_COLUMN indicates current data and
OLD_COLUMN indicates recent historical data
when a new record getting loaded source data is always
loded in NEW_COLUMN in target
when a record is midified target NEW_COLUMN is updated in
target OLD_COLUMN and source data is updated in target
NEW_COLUMN.
| Is This Answer Correct ? | 17 Yes | 1 No |
scd1 ---->will contain only the updated data(ie it contains
the newly entered data + updates of historic data)it dose
not maintain historic data
scd2 ---->it contains the updated data and the historic data
(full history)
scd3 ----->it contains updated data and historic data
partially(means it may contain the records of the last
6months i think)
| Is This Answer Correct ? | 3 Yes | 9 No |
scd 1:It wont implement the new change.It always contains
the historic data alone.
scd 2:It will replace or overwrite the existing record.It
will not contain the historic data.But it has surrogate key.
scd 3:It contains both the old data and a new record with
the modified information and has additional columns like
"effective start date and end date" or "version no".
Please correct me if i am wrong
| Is This Answer Correct ? | 0 Yes | 20 No |
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