Solving Procedure with no parameters

问题

Hey guys just here to see if you guys can help me solve this Procedure problem I am running into. Long story short I made a new table called

Create Table ClientHistoricalPurchases(
ClientID varchar2(6) constraint clientidhistorical references Clients,
DistinctProducts number (9),
TotalProducts number(9), 
TotalCost number (9,2),
Primary Key (ClientID));

And I want to populate/update this table by running a procedure that reads primarily from the following table:

create table OrderDetails(
OrderID varchar2(6) CONSTRAINT orddetpk PRIMARY KEY,
ProductID varchar2(6) CONSTRAINT prdfk REFERENCES Products ,
UnitPrice number(10,2),
Quantity number(4),
Discount number(3),
ShippingDate date);

I do a couple of joins with two more tables called Orders and Clients but those are trivial joins using the Primary Key's/FK.

So the goal of this procedure is that when I run it I want to loop through order details and I want to calculate the distinct amount of products bought by a Client, the total products and the total purchase amount and I want to update an existing record with the new values if its in the new ClientHistoricalPurchases table if not I want to add a new record for it. So this is what I wrote but its giving me errors:

Create or Replace Procedure Update_ClientHistPurch as

Cursor C1 is 
Select orderid, orders.clientid, productid, unitprice, quantity, discount
from orderdetails
Inner join orders on orderdetails.orderid = orders.clientid
for update of TotalCost;

PurchaseRow c1%RowType;
DistinctProducts orderdetails.quantity%type;
TotalProducts orderdetails.quantity%type;
ProposedNewBalance orderdetails.unitprice%type;

Begin
Begin
Begin
Begin
Open C1;
Fetch c1 into PurchaseRow;

While c1% Found Loop 
Select count(distinct productid)
into DistinctProducts
from orderdetails
Inner join orders on orderdetails.orderid = orders.orderid
Inner join clients on orders.clientid = clients.clientid
where clients.clientid = purchaserow.clientid;
end;

Select count(ProductID)
into TotalProducts
from orderdetails
Inner join orders on orderdetails.orderid = orders.orderid
Inner join clients on orders.clientid = clients.clientid
where clients.clientid = purchaserow.clientid;
end;

Select sum((unitprice * quantity) - discount)
into ProposedNewBalance
from orderdetails
Inner join orders on orderdetails.orderid = orders.orderid
Inner join clients on orders.clientid = clients.clientid
where clients.clientid = purchaserow.clientid;
end;

If purchaserow.clientid not in ClientHistoricalpurchases.clientid then
insert into ClientHistoricalPurchases values    (purchaserow.clientid,DistinctProducts, TotalProducts, ProposedNewBalance);
End if;

If purchaserow.clientid in ClientHistoricalPurchases.clientid then
Update Clienthistoricalpurchases
set clienthistoricalpurchases.distinctproducts = distinctproducts,    clienthistoricalpurchases.totalproducts = totalproducts,    clienthistoricalpurchases.totalcost = ProposedNewBalance
    where purchaserow.clientid = clienthistoricalpurchases.clientid;
end if;
end loop;
end;

Errors are the following:

Error(27,4): PLS-00103: Encountered the symbol ";" when expecting one of the following: loop The symbol "loop" was substituted for ";" to continue.
Error(33,7): PLS-00103: Encountered the symbol "JOIN" when expecting one of the following: , ; for group having intersect minus order start union where connect

Any help is appreciated guys. Thanks!

回答1:

In addition to the comments and answers you've already been given, I believe you have massively overcomplicated your procedure. You're doing things very procedurally, rather than thinking in sets as you should be. You are also getting the aggregated columns in three queries that are essentially identical (e.g. same tables, join conditions and predicates) - you could combine them all to get the three results in a single query.

It looks like you're trying to insert into the clienthistoricalpurchases table if a row doesn't already exist for that client, otherwise you update the row. That immediately screams "MERGE statement" to me.

Combining all that, I think your current procedure should contain just a single merge statement:

MERGE INTO clienthistoricalpurchases tgt
  USING (SELECT clients.client_id,
                COUNT(DISTINCT od.productid) distinct_products,
                COUNT(od.productid) total_products,
                SUM((od.unitprice * od.quantity) - od.discount) proposed_new_balance
         FROM   orderdetails od
         INNER  JOIN orders
         ON     orderdetails.orderid = orders.orderid
         INNER  JOIN clients
         ON     orders.clientid = clients.clientid
         GROUP BY clients.client_id) src
  ON (tgt.clientid = src.client_id)
WHEN NOT MATCHED THEN
  INSERT (tgt.clientid,
          tgt.distinctproducts,
          tgt.totalproducts,
          tgt.totalcost) 
  VALUES (src.clientid,
          src.distinct_products,
          src.total_products,
          src.proposed_new_balance)
WHEN MATCHED THEN
  UPDATE SET tgt.distinctproducts = src.distinct_products,
             tgt.totalproducts = src.total_products,
             tgt.totalcost = src.proposed_new_balance;

However, I have some concerns over your current logic and/or data model.

It seems like you're expecting at most one row per clientid to appear in clienthistoricalpurchases. What if a clientid has two or more different orders? Currently you would overwrite any existing row.

Also, do you really want to apply this logic across all orders every single time it gets run?