Question

I have two selection queries and i want to select values from both and have a new query.
I tried to join them but I don’t get the information i want to.

The first query that I have is the one below:

 SELECT InWarehouse.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity, 
      NZ(SUM(InWarehouse.quantity),0) AS quant
 FROM drugs 
      LEFT JOIN (SELECT drug_id, 
                        expiry_date, 
                        SUM(in_quant - out_quant) AS quantity 
                FROM warehouse GROUP BY drug_id, expiry_date)  
 AS InWarehouse ON 
      InWarehouse.drug_id = drugs.id
      GROUP BY InWarehouse.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity;

And the second one is:

 SELECT InPharmacy.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity,
      NZ(SUM(InPharmacy.quantity), 0) as quant
 FROM (drugs
 LEFT JOIN (SELECT drug_id, expiry_date, SUM(in_quant - out_quant) as quantity
            FROM pharmacy
            GROUP BY drug_id, expiry_date) as InPharmacy
 ON InPharmacy.drug_id = drugs.id)

 GROUP BY  InPharmacy.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity;

I want to get the:

InWarehouse.expiry_date, 
drugs.active_substance, 
drugs.strength, 
drugs.strength_type, 
drugs.dosage_form, 
drugs.minimum_quantity,
InWarehouse.quantity + InPharmacy.quantity,
InPharmacy.expiry_date
GROUP BY InWarehouse.expiry_date = InPharmacy.expiry_date

Any help please?

Answer 1

You can just put the two queries as subquery of a main query :

SELECT InWarehouse.expiry_date, 
t1.active_substance, 
drugs.strength, 
drugs.strength_type, 
drugs.dosage_form, 
drugs.minimum_quantity,
InWarehouse.quantity + InPharmacy.quantity,
InPharmacy.expiry_date
FROM (SELECT InWarehouse.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity, 
      NZ(SUM(InWarehouse.quantity),0) AS quant
 FROM drugs 
      LEFT JOIN (SELECT drug_id, 
                        expiry_date, 
                        SUM(in_quant - out_quant) AS quantity 
                FROM warehouse GROUP BY drug_id, expiry_date)  
 AS InWarehouse ON 
      InWarehouse.drug_id = drugs.id
      GROUP BY InWarehouse.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity  
) t1
JOIN (  SELECT InPharmacy.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity,
      NZ(SUM(InPharmacy.quantity), 0) as quant
 FROM (drugs
 LEFT JOIN (SELECT drug_id, expiry_date, SUM(in_quant - out_quant) as quantity
            FROM pharmacy
            GROUP BY drug_id, expiry_date) as InPharmacy
 ON InPharmacy.drug_id = drugs.id)

 GROUP BY  InPharmacy.expiry_date, 
      drugs.active_substance, 
      drugs.strength, 
      drugs.strength_type, 
      drugs.dosage_form, 
      drugs.minimum_quantity ) t2
 ON t1.active_substance = t2.active_substance

I have used the active_substance field as a key to join the two table, if not appropriate you can choose the more appropriate set of columns , however the technique is two put the two dinstinct query as subquery of a main one and JOIN them in the proper way …