Cross Group By and Max Date Script - sql

Question

I'm writing a script to pull a Group By and a MAX(CreatedOnDate) from two different tables but only return where table1's MAX(CreatedOnDate) is greater than table2's MAX(CreatedOnDate).
For example;
select MasterId, max(createdon) --Master id + latest product generated date
from product
group by MasterId
select contactId, max(createdon) --Contact id + latest edit date for that contact
from contactEdit
group by contactId
from contactEdit ce
join contactmaster cm
on ce.contactId = cm.contactid
join product p
on p.MasterId = cm.MasterId
Between these two tables there is a contactMaster table, the join of which is above also. I want to find a list of all Contacts who have had Edits made since the last Product was created relating to that Contact.
Something like;
where max(ce.createdon) > max(p.createdon)

Answer 1

i am not quite sure what your tables look like and what exactly you are trying to achieve, so this is a bit of a guess.
what you want to do is group the tables in subselects and then compare the maxdates:
with ce as (
select MasterId, max(createdon) maxco --Master id + latest product generated date
from product
group by MasterId
)
, prod as (
select contactId, max(createdon) maxco --Contact id + latest edit date for that contact
from contactEdit
group by contactId
)
, cm as (
select contactId, masterId, max(createdon) maxco --Master id + latest product generated date
from contactmaster
group by contactId, masterId
)
select contactId
from ce
join cm
on ce.contactId = cm.contactid
join product p
on p.MasterId = cm.MasterId
where ce.maxco > prod.maxco