如何使用SQL以整数的总和降序排序

Question

I'm creating a website in which I have to use PHP to pull out of a MySQL database and for this project I need to SELECT Total sales by customerName ORDER BY Total sales DESCending from my table. This is my table (the "sales" table):

I need to have it output this to a table (but it is the actual information not just "Customer" or "Total Sales"):

<tr>
    <td>Customer</td>
    <td>Total Sales</td>
    <td>Time of Sale</td>
    <td>Sales Department</td>
    <td>Item Sold</td>
    <td>Number of Items Sold</td>
    <td>Cost per Item</td>
    <td>Sales Person</td>
</tr>;

So basically I need to know how to have an SQL statement that pulls the information out of the table called "sales" for every saleItem with the customerName first, then the total (summation) (not just the number of items for that specific saleItem , it has to be every item that the customer has bought) numberOfItems that the customer has bought, then the saleDTM (time of the sale), then the saleDept (the sale department), then the saleItem (the item sold), then the numberOfItems (the number of items sold for the type of saleItem ), then the costPerItem (the cost of the saleItem ), then finally the salesPerson (the person that sold the saleItem ). All of that has to be ordered by the total (every item bought by the customer, not just the number of items bought for a specific saleItem ) numberOfItems that the customer has bought. How do I do that SQL statement?

Answer 1

You should be able to get the total sales per sales person with something along these lines.

select salesPerson, sum(numberOfItems * costPerItem) as total_sales
from sales
group by salesPerson
order by total_sales desc;

But there's no way to join that back to the sales table to give you, say, "time of sale" or "sales department". It just doesn't make sense.

Total sales per customer is similar, but it's also a different thing. (In your question, you refer to both "total sales per salesperson" and "total sales per customer".) The individual details--time of sale, sale department, etc--are yet another thing. You seem to be talking about three different kinds of reports, but maybe you know something the rest of us don't.