Answer / abhinaw prakash

surrogate key is used to avoid the critical column.critical
column means the column which makes the analysation or data
wrong for example assume one customer table
cust_id(p.k) cust_name amount loc
1 jones 1000 hyd
he purchase the product in hyd by 1000/- if he again
purchase by 2000/- in pune not in hyd.then we have to
create another record in that table with same cust_id but
here cust_id is having primary key so we are unable to
create a new record for suppose if u update the record u
got the wrong information as
1 jones 3000 pune
so eliminating this we are maintian the another column like
cust_no as surrogate key (unique value)and removes p.k in
cust_id.surrogate key is like an index.

Answer / vijaya

surrogate is acts as a primary key. some times we want to
maintain historical information of particular product or
anything. for eg, a product costs 20rs in the month of may
and next month it costs 25rs. in this case if we want to
maintain both records with same product_id then it cant be
possible if product_id is primary key. In this case we use
concept of surrogate key. like
skey prod_id price month
1 101 20 may
2 101 25 june

in informatica this concept is used in update strategy.

Answer / mahesh manam

The main purpose of SURROGATE KEY is:

--> If you want to store the multiple records
for example:
In one general store customer id is primary key ,
If the customer change his address or phone number .
But now our requeriment is like to store all the data along
with old


-->If you are using duplicate records with out using
SURROGATE KEY like as follows:

ID NAME LOC
1 Mahesh Chennai
1 Mahesh Hyderabad


In above case if you are work with any dimmension model it
is not support to use this table. So, we need to maintain
Primary Key in each table.

-->Surrogate key is a key in that table use as a primary
key in the table to do joininng to another

-->Surrogate is very usefull and Quickly
If you are using any huge amount of data and you need to
retrive the queries which is usefull to your bussiness

how can import the data from the flat files?

2 Answers  

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