sql - Return distinct rows after averaging on group -

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i have table mytable looks 

periodenddate tottermloans companyname 2009-09-30    na           abb 2009-09-30    5.38         abb 2009-09-30    4.34         abb 2009-12-31    5.6          abb 2009-12-31    5.6          abb 2009-12-31    5.6          abb 2010-03-31    5.47         abb 2010-03-31    5.47         abb 2010-03-31    5.0          abb

i wish group year , average of tottermloans each year, query repeated rows:

select year(periodenddate), avg(tottermloans), companyname  mytable group year(periodenddate)

which gives 

   year(periodenddate) avg(tottermloans) companyname    2009                 5.304             abb    2009                 5.304             abb    2009                 5.304             abb    2010                 5.313             abb    2010                 5.313             abb    2010                 5.313             abb

i like

   year(periodenddate) avg(tottermloans) companyname    2009                 5.304             abb    2010                 5.313             abb

do have use sub queries this? thank you

select            year(periodenddate), avg(tottermloans), companyname               mytable group          year(periodenddate), companyname

the distinct keyword can used on select statements remove duplicated results.


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