SQL Server: value divided by rolling sum of last four values? -


how can value divided last 4 values in sql server 2014?

example. how can valuedivbylastfourvalues field value field?

month|value| valuedivbylastfourvalues | ---------------------------------------   1  |  1  |            1             |   2  |  1  |            1/2           |   3  |  2  |            2/4           |   4  |  2  |            2/6           |   5  |  1  |            1/6           |   6  |  7  |            7/12          |   7  |  4  |            4/14          |

bad trial

select      customer     ,month     ,net_value_m / sum(net_value_m) 'net_value_m_prop_by_year'     data group  left(month,4)         ,customer         ,month         ,net_value_m order net_value_m_prop_by_year

if understand correctly:

select customer, month,        (net_value_m /         sum(net_value_m) on (order month rows between 4 preceding , current row)        ) net_value_m_prop_by_year data;

this uses window function sum values in current row , preceding 4 rows.


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