Firstly this isn’t a Perl question, but more importantly you need to let us know what you are trying to do and what is going wrong. To me it looks like you are simply trying to pull out some data from two tables and hold them in a temp table. If so then try this

SELECT Time_ref, 
       Time_instance, 
       Geo_class, 
       Aggregated_area, 
       Super_classed_disease_cat, 
       Cause, 
       Constraint_ref, 
       Sex, 
       Sex_code, 
       Age_start, 
       Age_end, 
       Age_range, 
       Sum_count = SUM(G.Converted_person_count)   
INTO #tmp_G_P_M_CC                                                
FROM  Geo_postaggregated_mortality_count_with_cause_catagory_SPLIT G,
Time_definition_SPLIT T                                           
WHERE T.Key_m >= 1 
  AND G.Time_instance = T.Instance_tag
GROUP BY G.Time_ref, 
         G.Time_instance, 
         G.Geo_class, 
         G.Aggregated_area, 
         G.Super_classed_disease_cat, 
         G.Cause, 
         G.Constraint_ref, 
         G.Sex, 
         G.Sex_code, 
         G.Age_start, 
         G.Age_end, 
         G.Age_range
[download]

Note that this assumes that Time_definition_SPLIT is an integer. If this is way off then you need to give more information