how to use an aggregate function
От | ggunning@esatclear.ie (jmsmithe) |
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Тема | how to use an aggregate function |
Дата | |
Msg-id | de0fa271.0305170818.5972e18e@posting.google.com обсуждение исходный текст |
Ответы |
Re: how to use an aggregate function
|
Список | pgsql-sql |
Hello Imagine if you would if I had a database like this: DROP TABLE Customer; CREATE TABLE Customer( CustomerID int, Cname varchar(10), City varchar(10), PRIMARY KEY(CustomerID) ); DROP TABLE Item; CREATE TABLE Item( ItemID int, UnitPrice int, PRIMARY KEY(ItemID) ); DROP TABLE AOrder; CREATE TABLE AOrder( AOrderID int, Odate date, CustomerID int, Ird_Amt int, PRIMARY KEY(AOrderID), FOREIGN KEY(CustomerID) REFERENCES Customer(CustomerID) ); DROP TABLE OrderItem; CREATE TABLE OrderItem( AOrderID int, ItemID int, Qty int, PRIMARY KEY(AOrderID, ItemID), FOREIGNKEY(AOrderID) REFERENCES AOrder(AOrderID), FOREIGN KEY(ItemID) REFERENCES Item(ItemID) ); DROP TABLE Warehouse; CREATE TABLE Warehouse( WarehouseID int, Wcity varchar(10), PRIMARY KEY(WarehouseID) ); DROP TABLE Shipment; CREATE TABLE Shipment( AOrderID int, WarehouseID int, ShipDate date, PRIMARY KEY(AOrderID, WarehouseID), FOREIGN KEY(AOrderID) REFERENCES AOrder(AOrderID), FOREIGN KEY(WarehouseID) REFERENCES Warehouse(WarehouseID) ); INSERT INTO Customer VALUES(1, 'Jack', 'NeverLd'); INSERT INTO Customer VALUES(2, 'Jill', 'Wall'); INSERT INTO Customer VALUES(3, 'Emma', 'Desolat'); INSERT INTO AOrder VALUES(1, '1/1/2003', 1, 3); INSERT INTO AOrder VALUES(2, '1/1/2003', 3, 3); INSERT INTO Item VALUES(1, 5); INSERT INTO Item VALUES(2, 5); INSERT INTO Item VALUES(3, 15); INSERT INTO OrderItem VALUES(1, 1, 1); INSERT INTO OrderItem VALUES(1, 2, 5); INSERT INTO OrderItem VALUES(1, 3, 15); INSERT INTO OrderItem VALUES(2, 1, 2); INSERT INTO OrderItem VALUES(2, 2, 5); INSERT INTO Warehouse VALUES(1, 'Water fall'); INSERT INTO Warehouse VALUES(2, 'Fall vill'); INSERT INTO Shipment VALUES(1, 2, '1/1/2002'); INSERT INTO Shipment VALUES(2, 1, '1/1/2002'); How would I List the name of customers who have paid an average of more then $6. Produce a listing Cname, Avg_Paid All I can think of is this. SELECT Customer.Cname, AVG(Item.UnitPrice) AS Avg_Paid FROM Customer JOIN AOrder ON Customer.CustomerID = AOrder.CustomerID JOIN OrderItem ON AOrder.AOrderID = OrderItem.AOrderID JOIN Item ON OrderItem.ItemID = Item.ItemID GROUP BY Customer.Cname ; I can't figure out how to limit it to over $6? Thanks for any help.
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