oracle - Select First Row of Every Group in sql -

this question has answer here:

• fetch row has max value column 31 answers

i have 2 tables .

1-> sm_employee

 (1) employeeid     (2) roleid  (3) storeid 

2-> sm_salesrepworkflow

 (1) workflowid  (2) salesrepid   foreign key employeeid  (3) quantityassigned  (4) quantityleft  (5) month   (6) year 

by these tables need select first row of every salesrep details sm_salesrepworkflow order salesrepid currentmonth , currentyear.

example

workflowid salesrepid quantityassigned quantityleft month year

wf_101 : emp_101 : 100 : 90 : may : 2013
wf_101 : emp_102 : 100 : 100 : may : 2013
wf_101 : emp_103 : 100 : 80 : may : 2013
wf_102 : emp_101 : 100 : 70 : may : 2013

so result want

wf_101 : emp_101 : 100 : 90 : may : 2013
wf_101 : emp_102 : 100 : 100 : may : 2013
wf_101 : emp_103 : 100 : 80 : may : 2013

so there can many workflow salesrep. want first 1 every salesrep current month , year.

you can use row_number() function this:

select *   from(select workflowid, salesrepid, quantityassigned,               quantityleft, month, year               , row_number()                 on (partition salesrepid                           order workflowid) rownumber          sm_salesrepworkflow)  rownumber = 1; 

fiddle demo