Merge output as one - sql

Question

Select Category, Books.ISBN,
Orderitems.Quantity * (Books.Retail - Books.Cost) AS Category_Profit
From BOoks
INNER JOIN Orderitems
ON BOOKS.ISBN=ORDERITEMS.ISBN
Example output:
Category ISBN Category_Profit
Family life 1234 50
Family Life 1234 50
Family Life 1234 100
Fitness 4321 10
Fitness 4321 20
So forth and so forth,
How can I make the output calculate all the values for each category into one line?
I.e
Family Life 1234 200
Fitness 4321 30

Answer 1

Because you already have this as a starting point, use exactly what you have as a temp table, and pull data from that:
Select Category, ISBN, Sum(Category_Profit) From
(
select Category, Books.ISBN as ISBN,
Orderitems.Quantity * (Books.Retail - Books.Cost) AS Category_Profit
From Books
INNER JOIN Orderitems
ON BOOKS.ISBN=ORDERITEMS.ISBN
) temp
group by Category, ISBN
You organized the data really well, so implementing a sum on the Profit is easy. You group by Category and ISBN to get all unique pairs of those columns with the corresponding Profit.
If you do not want to use a sub-query you can sum in your query (but I feel it's something helpful to use my existing query as a sub-query before altering it, just to make sure it works:
select Category, Books.ISBN,
SUM(Orderitems.Quantity * (Books.Retail - Books.Cost)) AS Category_Profit
From Books
INNER JOIN Orderitems
ON BOOKS.ISBN=ORDERITEMS.ISBN
temp
group by Category, Books.ISBN

Answer 2

Group by can be used to solve your problem.
Note: In Group by clause , a set of table rows can be grouped based on certain columns and in the select clause either the group by columns or aggregate function(SUM,MIN,MAX,Count etc) on other columns can be shown.
Reference :
http://www.dofactory.com/sql/group-by
Use group by as is done below. Hope this solves the issue.
Select Category, Books.ISBN,
SUM(Orderitems.Quantity * (Books.Retail - Books.Cost)) AS Category_Profit
From BOoks
INNER JOIN Orderitems
ON BOOKS.ISBN=ORDERITEMS.ISBN
Group by Category,ISBN

Answer 3

Use GROUP_BY & SUM, Syntax :
SELECT column_name, SUM(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;
Refer: SQL GROUP_BY
On you table you may run :
Select Category, ISBN, Sum(Category_Profit) From Table1
group by Category, ISBN;
Table1:
Category ISBN Category_Profit
Family life 1234 50
Family Life 1234 50
Family Life 1234 100
Fitness 4321 10
Fitness 4321 20
Output:
| Category | ISBN | Sum(Category_Profit) |
|-------------|------|----------------------|
| Family life | 1234 | 200 |
| Fitness | 4321 | 30 |
Fiddle