January 7, 2010 at 11:42 am
What is the Difference Between cross apply and cross join
January 7, 2010 at 12:46 pm
You have posted your question in a SQL 2000 forum ... CROSS APPLY WAS introduced in SQL Server 2005 ...
For SQL 2000 CROSS JOINS exist and they exist in SQL 2005 as well ... so the difference is .. one exists one does not.
Now if you question pertains to SQL 2005 or 2008 use Books On Line for an explanation and sample code ....
January 8, 2010 at 6:58 am
CROSS JOIN returns a Cartesian product so if you have 10 rows in each table the query will return 100 rows, 1 row for each combination.
CROSS APPLY from BOL:
The APPLY operator allows you to invoke a table-valued function for each row returned by an outer table expression of a query. The table-valued function acts as the right input and the outer table expression acts as the left input. The right input is evaluated for each row from the left input and the rows produced are combined for the final output. The list of columns produced by the APPLY operator is the set of columns in the left input followed by the list of columns returned by the right input.
CROSS APPLY is similar to, but in most cased not the same as an INNER JOIN. When calling a TVF the TVF is called/executed for each row in the outer table/left input.
You pass one of the columns from the outer table to the function and the TVF returns the matching rows. You can also use APPLY to supply a value to "join" on a derived table. Here's a simple example of both CROSS JOIN and CROSS APPLY (the cross apply with the derived table in this example would be better written as an INNER JOIN and the Optimizer converts it to one):
-- create a table to run the function against
CREATE TABLE test2 (id INT, col1 CHAR(1))
GO
-- create the TVF
CREATE FUNCTION test (@id INT)
RETURNS @table TABLE (id INT, col1 CHAR(1))
AS BEGIN
INSERT INTO
@table
SELECT
*
FROM
test2 AS T
WHERE
id = @id ;
RETURN
END
GO
-- table variable for outer/left input
DECLARE @test1 TABLE (id INT, col1 CHAR(1))
-- insert test data
INSERT INTO
@test1 (id, col1)
SELECT TOP 10
ROW_NUMBER() OVER (ORDER BY OBJECT_ID),
CHAR(ROW_NUMBER() OVER (ORDER BY OBJECT_ID) + 60)
FROM
sys.all_columns AS AC
INSERT INTO
test2 (id, col1)
SELECT TOP 10
ROW_NUMBER() OVER (ORDER BY OBJECT_ID),
CHAR(ROW_NUMBER() OVER (ORDER BY OBJECT_ID) + 60)
FROM
sys.all_columns AS AC
-- cross join Cartesian product
SELECT
*
FROM
@test1 CROSS JOIN
test2
-- outer apply on a derived table
SELECT
*
FROM
@test1 AS one CROSS APPLY
(
SELECT
*
FROM
test2 AS two
WHERE
one.id = two.id
) AS test2
-- outer apply TVF
SELECT
*
FROM
@test1 AS one CROSS APPLY
dbo.test(one.id) ;
DROP TABLE test2 ;
GO
DROP FUNCTION dbo.test ;
If you SET STATISTICS IO ON you will see that the last query (CROSS APPLY to the TVF) has 10 scans because for each row in @test1 the TVF is being called and going out and scanning the test2 table.
Jack Corbett
Consultant - Straight Path Solutions
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January 11, 2010 at 12:10 am
Thank you Jack Corbett.
nice explanation and example
Balamurugan
March 24, 2011 at 12:08 pm
Y'all are welcome. I'm glad it made sense.
Jack Corbett
Consultant - Straight Path Solutions
Check out these links on how to get faster and more accurate answers:
Forum Etiquette: How to post data/code on a forum to get the best help
Need an Answer? Actually, No ... You Need a Question
June 19, 2014 at 12:57 pm
bitbucket-25253....wasted my time what a response
June 20, 2014 at 1:40 am
daniarchitect (6/19/2014)
bitbucket-25253....wasted my time what a response
If Bitbucket's explanation doesn't exactly meet your requirements, then simply ask what you need to know. Rudeness is unnecessary and unprofessional.
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden
June 20, 2014 at 9:27 am
daniarchitect (6/19/2014)
bitbucket-25253....wasted my time what a response
BWAA-HAA!!! Considering that you even went back and edited your response, I suspect you voluntarily wasted more time on your own that what you claim BitBucket did. 😉
--Jeff Moden
Change is inevitable... Change for the better is not.
December 23, 2015 at 3:04 pm
bitbucket-25253 (1/7/2010)
You have posted your question in a SQL 2000 forum ... CROSS APPLY WAS introduced in SQL Server 2005 ...For SQL 2000 CROSS JOINS exist and they exist in SQL 2005 as well ... so the difference is .. one exists one does not.
Now if you question pertains to SQL 2005 or 2008 use Books On Line for an explanation and sample code ....
That's a pretty jerk answer.
December 24, 2015 at 2:53 pm
That's a pretty jerk answer.
Sorry, but I don't agree. Maybe it could have been phrased differently, although I don't see anything wrong with it. But the help on this site is free. And it would be helpful if questions were appropriately addressed. It would also be helpful to know some little bit of research has been done.
December 24, 2015 at 4:27 pm
RonKyle (12/24/2015)
That's a pretty jerk answer.
Sorry, but I don't agree. Maybe it could have been phrased differently, although I don't see anything wrong with it. But the help on this site is free. And it would be helpful if questions were appropriately addressed. It would also be helpful to know some little bit of research has been done.
+1000. And the answer was much more helpful than what I was going to post and didn't, which would have been a LMGTFY response.
--Jeff Moden
Change is inevitable... Change for the better is not.
December 25, 2015 at 9:05 am
Jeff Moden (12/24/2015)
RonKyle (12/24/2015)
That's a pretty jerk answer.
Sorry, but I don't agree. Maybe it could have been phrased differently, although I don't see anything wrong with it. But the help on this site is free. And it would be helpful if questions were appropriately addressed. It would also be helpful to know some little bit of research has been done.
+1000. And the answer was much more helpful than what I was going to post and didn't, which would have been a LMGTFY response.
I also agree. If the SQL 2000 point was skipped, the next response would have been "Hey, your code sucks because it doesn't work on my SQL 2000 instance." No matter how it was phrased, it was correct. Then again, Books Online was available back in 2010 when the question was originally posted. I don't think SQL 2000 has changed much since then.
December 28, 2015 at 7:16 am
If the SQL 2000 point was skipped, the next response would have been "Hey, your code sucks because it doesn't work on my SQL 2000 instance."
A good point. Maybe he posted it in the correct forum. Given the way he phrased the question, I don't think so. But maybe not safe to assume.
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