SQL Server- Return Items Only When All Sub-Items Are Available - sql

Question

I have an Item table (denormalized for this example) containing a list of items, parts and whether the part is available. I want to return all the items for which all the parts are available. Each item can have a varying number of parts. For example:
Item Part Available
A 1 Y
A 2 N
A 3 N
B 1 Y
B 4 Y
C 2 N
C 5 Y
D 4 Y
D 6 Y
D 7 Y
The query should return the following:
Item Part
B 1
B 4
D 4
D 6
D 7
Thanks in advance for any assistance.

Answer 1

Here is one trick using Max() Over() Window aggregate Function
SELECT Item,
Part
FROM (SELECT Max([Available])OVER(partition BY [Item]) m_av,*
FROM yourtable) a
WHERE m_av = 'Y'
or using Group By and Having clause
Using IN clause
SELECT Item,
Part
FROM yourtable
WHERE Item IN (SELECT Item
FROM yourtable
GROUP BY Item
HAVING Count(*) = Sum(Iif(Available = 'Y', 1, 0)))
using Exists
SELECT Item,
Part
FROM yourtable A
WHERE EXISTS (SELECT 1
FROM yourtable B
WHERE A.Item = B.Item
HAVING Count(*) = Sum(Iif(Available = 'Y', 1, 0)))
using NOT EXISTS
SELECT Item,
Part
FROM yourtable A
WHERE NOT EXISTS (SELECT *
FROM yourtable B
WHERE A.Item = B.Item
AND B.Available = 'N')

Answer 2

I'd start with rephrasing the requirement - you want to return the items that don't have any parts that are not available. Once you put it like that, it's easy to translate the requirement to SQL using the not exists operator:
SELECT item, part
FROM parts a
WHERE NOT EXISTS (SELECT *
FROM parts b
WHERE a.item = b.item AND b.available = 'N')

Answer 3

Using window function does a single table read.
MIN and MAX window function
select *
from (
select
t.*,
max(available) over (partition by item) a,
min(available) over (partition by item) b
from your_table t
) t where a = b and a = 'Y';
COUNT window function:
select *
from (
select
t.*,
count(*) over (partition by item) n1
count(case when available = 'Y' then 1 end) over (partition by item) n2
from your_table t
) t where n1 = n2;

Answer 4

U can use NOT IN OR NOT EXISTS to achieve this
NOT EXISTS
Select item, part
from table as T1
where not exists( select 1 from tbl where item = t1.item and available = 'N')
NOT IN
Select item, part
from table
where item not in( select item from tbl where available = 'N')

Answer 5

I want to point out that the question in the text is: "I want to return all the items for which all the parts are available". However, your example results include the parts.
If the question is indeed that you want the items only, then you can use simple aggregation:
select item
from parts
group by item
having min(available) = max(available) and min(available) = 'Y';
If you indeed want the detail on the parts as well, then the other answers provide that information.

Answer 6

I do like it problems lend themselves well to being solved by infrequently used language features:
with cte as (
select * from (values
('A', 1, 'Y'),
('A', 2, 'N'),
('A', 3, 'N'),
('B', 1, 'Y'),
('B', 4, 'Y'),
('C', 2, 'N'),
('C', 5, 'Y'),
('D', 4, 'Y'),
('D', 6, 'Y'),
('D', 7, 'Y')
) as x(Item, Part, Available)
)
select *
into #t
from cte as c;
select *
from #t as c
where 'Y' = all (
select Available
from #t as a
where c.Item = a.Item
)
Here, we use a correlated subquery and the all keyword to see if all of the parts are available. My understanding is that, like exists, this will stop if it finds a counter-example.