Aggregation: database vs GAMS

*-------------------------------------------
* Aggregation
*-------------------------------------------

set
   y(year) /1990*2000/
   aggr_type(type) 'these quantities are aggregated directly' /
          'Area Harvested'             Ha
          'Production Quantity'        Tonnes
    /
;
parameter AggrCropData(cropgroup,region,y,type);

AggrCropData(cropgroup,region,y,aggr_type) =
     sum((cropmap(crop,cropgroup),regionmap(country, region),unit,flag),
             cropdata(country,crop,aggr_type,y,unit,flag));

*-------------------------------------------
* Recalculate Yield (Hg/Ha)
*-------------------------------------------

AggrCropData(cropgroup,region,y,'Yield')$AggrCropData(cropgroup,region,y,'Area Harvested') =
    1e5*AggrCropData(cropgroup,region,y,'Production Quantity') /
      AggrCropData(cropgroup,region,y,'Area Harvested')

---

--- Aggregation

---

useaggregation;

---

--- if target table exists, drop it

---

IFEXISTS(SELECT*FROMsys.objects  WHEREobject_id=OBJECT_ID('[dbo].[AggregatedData]')ANDtype='U')

DROPTABLEAggregatedData;

---

--- Step 1:

--- Aggregate Area and Production

---

SELECTC.CropGroup,R.Region,A.Element,A.[Year],Sum(A.Value)AS[Value]

INTOAggregatedData

FROMProduction_Crops_E_All_DataASA,

     cropmapASC,

     regionmapASR

WHERE

     A.ElementIn('Area Harvested','Production Quantity')And

     A.[Year]>='1990'AndA.[Year]<='2000'And

     A.Country=R.CountryAnd

     A.Item=C.Crop

GROUPBYC.CropGroup,R.Region,A.Element,A.[Year];

---

--- Step 2:

--- Recalculate Yield

---

INSERTINTOAggregatedData(CropGroup,Region,Element,[Year],[Value])

SELECTA.CropGroup,A.Region,'Yield',A.[Year], 1.0e5*A.[Value]/B.[Value]

FROMAggregatedDataASA,

     AggregatedDataASB

WHERE

     A.CropGroup=B.CropGroupAND

     A.Region=B.RegionAND

     A.[Year]=B.[Year]AND

     A.Element='Production Quantity'AND

     B.Element='Area Harvested'AND

     B.Value> 0;