How to update 1st record in a set of records with unique constrains?

[Arjun Damodar]

Hello,

Let below shown be the table which i need to update:

No C1 C2 C3 C4
1 A A A A
2 A A A A
3 A A B A
4 A B A A
5 A B A A
6 A B B A
7 B A A A
8 B A B A
9 B A B A
10 B A B A
11 B B B A


Here record 1 and record 2 are the same and so are the records 4 and 5 and also 8, 9 and 10. In This case what i want is i need to update the values of C3 in records 1,3,4,6,7,8 and 11. so that the in the end the records will look like below:

No C1 C2 C3 C4
1 A A A B
2 A A A A
3 A A B B
4 A B A B
5 A B A A
6 A B B B
7 B A A B
8 B A B B
9 B A B A
10 B A B A
11 B B B B

Please help me out here. Also, since i need to do this on a table with more than 500,000 records, processing time also is a constrain.

[debasisdas]

What is the logic that needs to be implemented for this entire process , or just some random update ?

[Arjun Damodar]

if we consider c1||c2||c3, then that would be a duplicate entry.

[Arjun Damodar]

Please find this excel useful: http://www.freewebs.com/arjundamodar...iqueUpdate.xls

In this if u consider C1, C2 and C3, the C4 is not updated when C1 + C2 + C3 forms a 2nd duplicate record. ie, 1st record will be updated in all cases.. but second or above wont be updated.