August 25, 2009 at 11:58 am
Hello all,
A colleague of mine showed me a query employing some methods of controlling query flow that I am not familiar with--in particular, the usage of the keywords inside, middle, and outside. Here is an example:
update outside
set OrderId = (select top 1 middle.OrderId from Orders middle
where OrderDate =
(select min(inside.OrderDate) from Orders inside where OrderTime > 0 and inside.CustomerId = middle.CustomerId and schedulestatus = 'D')
and outside.CustomerId = middle.CustomerId)
from CustomerTable outside
where (CustomerType = 'H' or CustomerType = 'C')
and not exists (select * from Orders where OrderId = outside.OrderId)
These keywords seem like useful things to understand. While I generally understand what the query above does, I am having trouble looking up reference material for the usage of these keywords. Does anyone know what the usage of these keywords is called generally (e.g. query control)? Also, can someone point me in the right direction in terms of reference material to read to understand these keywords? I would appreciate any help that anyone can give.
Thanks.
August 25, 2009 at 12:03 pm
cjohn5552 (8/25/2009)
Hello all,A colleague of mine showed me a query employing some methods of controlling query flow that I am not familiar with--in particular, the usage of the keywords inside, middle, and outside. Here is an example:
update outsideset OrderId = (select top 1 middle.OrderId from Orders middle
where OrderDate =
(select min(inside.OrderDate) from Orders inside where OrderTime > 0 and inside.CustomerId = middle.CustomerId and schedulestatus = 'D')
and outside.CustomerId = middle.CustomerId)
from CustomerTable outside
where (CustomerType = 'H' or CustomerType = 'C')
and not exists (select * from Orders where OrderId = outside.OrderId)
These keywords seem like useful things to understand. While I generally understand what the query above does, I am having trouble looking up reference material for the usage of these keywords. Does anyone know what the usage of these keywords is called generally (e.g. query control)? Also, can someone point me in the right direction in terms of reference material to read to understand these keywords? I would appreciate any help that anyone can give.
Thanks.
What you are calling keywords are actually table aliases.
August 25, 2009 at 12:04 pm
From what I see, these are not keywords as it is. The query is just Aliased using inside, outside and middle. You can replace those words with A, B and C and it will still work the same way.
You beat me to it Lynn 🙂
-Roy
August 25, 2009 at 12:06 pm
Oh wow! Thanks Lynn, all of a sudden, I thought they put new operators in sql server, again. Good to know they are only ol'aliases!
Cheers,
J-F
August 25, 2009 at 2:42 pm
Hahaha, that's funny. No wonder I was having trouble finding documentation for those "keywords". Sorry for the misunderstanding.
August 25, 2009 at 3:02 pm
cjohn5552 (8/25/2009)
Hahaha, that's funny. No wonder I was having trouble finding documentation for those "keywords". Sorry for the misunderstanding.
No problem, it's why we are here, to help clear up misunderstandings and increase others knowledge.
August 25, 2009 at 3:34 pm
Lynn Pettis (8/25/2009)
cjohn5552 (8/25/2009)
Hahaha, that's funny. No wonder I was having trouble finding documentation for those "keywords". Sorry for the misunderstanding.No problem, it's why we are here, to help clear up misunderstandings and increase others knowledge.
And, occasionally learn something new ourselves - which is something I do every day :hehe:
Jeffrey Williams
“We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”
― Charles R. Swindoll
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