SCD

Slow changing dimension

It can be defined as the dimension which changes in the course of time.  It is important in the database to track the changing data.  It is a term is data management and data ware.

For example a company has a customer who lives in Texas . When he plans to move to California the data in location is changed.  The database of the company has to update the record in every changing records.

Slow changing dimension cha be divided into three basic types:

Type 1:

In this type  the changed data are overwritten. The database doesn’t keep track of old data.

Here in the table below the old location Texas is overwritten with new record California.

Customer name	Type of policy	Date of policy	location
Mr B	Full coverage	25-jan-13	CA

Type 2:

In this type of scd the database keep track on old data.

Customer name	Type of policy	Date of policy	location
Mr.B	Full coverage	4-mar-12	tx
Mr.B	Full coverage	25-jan-13	ca
Mr .B	Liability	16-aug-14	va
Mr.B	Full coverage	20-dec-14	ny

Type 3 :

In this type of scd database keep track of last two records.

Customer name	Type of policy	Date of policy	Location
Mr.B	Liability	16-aug-14	Va
Mr.B	Full coverage	20-dec-14	ny