Question

Say I have a table like this in my MsSql server 2005 server

Apples
 + Id
 + Brand
 + HasWorms

Now I want an overview of the number of apples that have worms in them per brand.
Actually even better would be a list of all the apple brands with a flag if they are unspoiled or not.

So if I had the data

ID| Brand        | HasWorms
---------------------------
1 | Granny Smith | 1
2 | Granny Smith | 0
3 | Granny Smith | 1
4 | Jonagold     | 0
5 | Jonagold     | 0
6 | Gala         | 1
7 | Gala         | 1

I want to end up with

Brand        | IsUnspoiled
--------------------------
Granny Smith | 0
Jonagold     | 1
Gala         | 0

I figure I should first

select brand, numberOfSpoiles = 
    case
        when count([someMagic]) > 0 then 1
        else 0
     end
from apples
group by brand

I can’t use a having clause, because then brands without valid entries would dissapear from my list (I wouldn’t see the entry Gala).
Then I thought a subquery of some kind should do it, but then I can’t link the apple id of the outer (grouped) query to the inner (count) query…

Any ideas?

Answer 1

SQL server version, I did spoiled instead of unspoiled, this way I could use the SIGN function and make the code shorter

table + data (DML + DDL)

create table Apples(id int,brand varchar(20),HasWorms bit)

insert Apples values(1,'Granny Smith',1)
insert Apples values(2,'Granny Smith',0)
insert Apples values(3,'Granny Smith',1)
insert Apples values(4,'Jonagold',0)
insert Apples values(5,'Jonagold',0)
insert Apples values(6,'Gala',1)
insert Apples values(7,'Gala',1)

Query

select brand, IsSpoiled = sign(sum(convert(int,hasworms)))
from apples
group by brand

Output

brand   IsSpoiled
---------------------- 
Gala    1
Granny Smith    1
Jonagold    0