I don't think I've ever used cross join 
. What seems to happen is cross join would therefore select every user, and add to it every user_desc; there's no actual link between the two so you couldn't work out what job the user had.
I.e.:
Users
Users_Desc:
Cross join result:
Notice that each user is duplicated as it contains rows for all jobs.
With an inner join:
http://weblogs.sqlteam.com/jeffs/jeffs/archive/2005/09/12/7755.aspx
http://en.wikipedia.org/wiki/Join_(SQL)
. What seems to happen is cross join would therefore select every user, and add to it every user_desc; there's no actual link between the two so you couldn't work out what job the user had.I.e.:
Users
Code:
name staffnumber
-------------------------------------------------- -----------
John 1000002
Bananaman 1000005Users_Desc:
Code:
staffnumber job
----------- --------------------------------------------------
1000002 Engineer
1000005 SuperheroCross join result:
Code:
name staffnumber staffnumber job
-------------------------------------------------- ----------- ----------- --------------------------------------------------
John 1000002 1000002 Engineer
Bananaman 1000005 1000002 Engineer
John 1000002 1000005 Superhero
Bananaman 1000005 1000005 SuperheroNotice that each user is duplicated as it contains rows for all jobs.
With an inner join:
Code:
name staffnumber staffnumber job
-------------------------------------------------- ----------- ----------- --------------------------------------------------
John 1000002 1000002 Engineer
Bananaman 1000005 1000005 Superherohttp://weblogs.sqlteam.com/jeffs/jeffs/archive/2005/09/12/7755.aspx
http://en.wikipedia.org/wiki/Join_(SQL)
