如何在 Mysql 计算中使用别名

Question

I created the alias NumDrums from the count operation. I would like to use this alias again to create another alias UnitTotal, a calculated column. When running the query I get the following error:

Error executing query: #42S22Reference 'NumDrums' not supported (reference to group function)

Select
    customers.CustCompanyName,
    products.ProdUnNum,
    customers.CustGenerator,
    products.ProdID,
    products.ProdSize,
    products.ProdUnitName,
    COUNT(*) as NumDrums,
   (SELECT NumDrums) * products.ProdSize as UnitTotal
   
From
    drums Inner Join
    orders On drums.OrderID = orders.OrderID Inner Join
    manifests On orders.ManifestID = manifests.ManifestID Inner Join
    customers On drums.CustID = customers.CustID
            And orders.CustID = customers.CustID Inner Join
    products On drums.ProdID = products.ProdID
Group By
    customers.CustCompanyName,products.ProdUnNum
Order by
customers.CustCompanyName

Answer 1

Just use COUNT(*) * products.ProdSize, thanks to user Thallius