What is a surrogate key?Why we use it in a mapping?Pl give
an example.
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Answer / saradhi
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.
| Is This Answer Correct ? | 12 Yes | 1 No |
surrogate key is a System generated Key ( Artificial
key ),Every join between dimension tables and fact tables
in a data warehouse environment should be based on
surrogate keys, not natural keys.
There are still more reasons to use surrogate keys. One of
the most important is the need to encode uncertain
knowledge. You may need to supply a customer key to
represent a transaction, but perhaps you donýt know for
certain who the customer is. This would be a common
occurrence in a retail situation where cash transactions
are anonymous, like most grocery stores.
What is the customer key for the anonymous customer?
Perhaps you have introduced a special key that stands for
this anonymous customer. This is politely referred
to as a "hack."
| Is This Answer Correct ? | 6 Yes | 1 No |
Answer / venkadesh
IT IS UNIQUE KEY AND ITS USED FOR COMPARING THE EMPLOYEE DETAILS
| Is This Answer Correct ? | 0 Yes | 5 No |
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my sourse is like id name sal--1 aa 1000 ,2 bb 2000, 3 cc 3000 4 dd 4000, 5 ee 6000 , 6 ff 7000 and so on but myrequirement is like this id name sal up_sal,1 aa 1000 null,2 bb 2000 1000, 3 cc 3000 2000 4 dd 4000 3000, 5 ee 5000 4000 , 6 ff 6000 50000 and so on so how can i get it plez reply for this as soon as possible , thanks in advanced
if soource is having 10 records how will u insert 20 records to target
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