sql server - Merge duplicate records and update its table -

can me problem sql query?

i want merge/(sum if necessary) data of customer duplicate customer mame.

in project, find out customer has been duplicated using code:

select firstname, lastname, count(1) repeatedcount  customer group firstname, lastname having count(1) > 1 

how can update customer table 1 customer record , sum of totalsales , totavisits in 1 record only.

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sample data:

firstname  lastname   totalsales     totalvisits ---------- ---------- -------------- ----------- michelle   go         0.00           0 michelle   go         6975.00        1 michelle   go         1195.00        1 michelle   go         9145.00        3 michelle   go         57785.00       5 michelle   go         5845.00        1 michelle   go         0.00           0 michelle   go         0.00           0 

expected output:

firstname  lastname   totalsales     tolalvisits ---------- ---------- -------------- ----------- michelle   go         80945.00       11 

you have use aggregate function sum group by.

query

select firstname,lastname, sum(totalsales) totalsales, sum(totalvisits) totalvisits customer group firstname,lastname; 

and better practice suggest add column customerid unique.
can group easily.

sql fiddle