Results 1 to 4 of 4
  1. #1
    Join Date
    Nov 2011
    Posts
    8

    Not sure where to post this question

    Hello all, thanks for taking the time to read my post. First off I'm learning about cartesian products and I can only ever find very basic examples such as:

    A = {red, blue}
    B = {shirt, hat}

    A x B = {(red shirt), (red hat), (blue shirt), (blue hat)}

    So the cartesian product written mathematically is:

    A x B {(a, b): a ∈ A, b ∈ B} ?

    But that's all I can find on examples really on youtube and stuff nothing really goes more indepth. Last years exam paper had this question and I'll probably get a similar question this year. Could anyone explain how I would go about answering it?
    Attached Thumbnails Attached Thumbnails Untitled.png  

  2. #2
    Join Date
    Apr 2002
    Location
    Toronto, Canada
    Posts
    20,002
    belongs in Database Concepts & Design - dBforums

    apply your AxB method and simply write out all combinations from those two tables

    do you know what a natural join is?
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  3. #3
    Join Date
    Nov 2011
    Posts
    8
    No not really. You say apply my A x B method to those tables but the tables have so much more data in them than the simple problem I answered. Can you demonstrate how you would begin to pair these up?

  4. #4
    Join Date
    Apr 2002
    Location
    Toronto, Canada
    Posts
    20,002
    let's say the tables are A (a1,a2) and B (b1,b2)

    the cartesian product would be AxB = { (a1,a2,b1,b2): (a1,a2) ∈ A, (b1,b2) ∈ B }

    simple, innit
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •