SCD types

scd's are three types
scd1----no history
scd2-----/
/------scd2.1----version mechanism
/------scd2.1----date mechanism
/------scd2.3----status mechanism
scd3

Slowly Changing Dimensions (SCDs) :Slowly Changing Dimensions (SCDs) are dimensions that have data that changes slowly, rather than changing on a time-based, regular schedule.
* 1 Type 0
* 2 Type 1
* 3 Type 2
* 4 Type 3
* 5 Type 4
* 6 Type 6 / Hybrid

There are 3 types of slowly changing dimensions
Out of which type1 will not retain any history and its a direct update of the changed record
whereas type2 retains the history of the same and Type3 retains the latest history of the record

SCD are of following types:
type 1 - updates changes without preserving history
type 2 - stores history data by maintaining versions of the updated data
type 3 - either stores current and previous version of the data OR current and original version of the data
type 4 - stores history data by maintaining a separate history table
type 6 (type 2 + type 3) - stores history data by maintaining a flag which indicates if it is an active record or a history record AND separate date fields are maintained to recognize history data

Slowly changing dimensions are 3 types. In scd-1 new data is inserted by deleting old one. so latest information is stored.
In scd-2 we can maintain history of data for a particular item. new data is existed as a new row with previous data.
In scd-3 we can add one column to previous information, and it maintains latest information and just its previous value. not complete history.