Re: Tables and foreign keys
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On Dec 26, 2011, at 1:57 AM, Amit Tandon wrote:
Dear KarlForeign key is a good option (provided you use InnoDB database) to automatethe deletion/updation of cart details when you remove cart.Besides 1:1 cardinality is good or bad can only be decided on the semanticsof your tables.As a an aside, if it is 1:1 cardinality, then you can probably merge thetwo tables ============ regds amit"The difference between fiction and reality? Fiction has to make sense."On Mon, Dec 26, 2011 at 12:38 PM, Karl DeSaulniers <karl@xxxxxxxxxxxxxxx >wrote:Hello all, I have two database tables. Cart and a cartdetails.I want the information for the cartdetails to be based on/ autofilled infofrom cart.I want the ability to delete from cart and cartdetails to automaticallyclear as well. Would a foreign key be best suited for this? What kind of cardnaility would I use 1:1 ? Hope I make sense. Hope everyone had a great holidays! Best, Karl DeSaulniers Design Drumm http://designdrumm.com
Thanks Amit for the reply.Ok, so if you can not merge the two tables, then it is not a 1:1 relationship?
EG: (table)CART: cartID - PRIMARY username firstname lastname product long description quantity options price (table)CARTDETAILS: cartdetailsID cartID - Foreign Key (Unique) product short description (taken from long des. in CART) quantity options price Is this a 1:1 if the key is between the two cartID's? What is actually happening when I make a foreign key?What does the foreign key cover? Just the row its linked to or the whole table?
For this structure I would like, in order for their to be cartdetails, there should be a cart. If there is a cart then a cartdetails needs to automatically/ progmatically generate. (I think I read somewhere that MySQL is capable of doing this before sending back responses. Please correct me if I am wrong or if its unrelated.)
What kind of relation is that?Also, if you or someone could explain what these cardinality rules mean. What..
0 or 1 does? 1+ does? 0,1+ does? Many (kind-of figured this one out, perhaps not.) etc..I think that would help me greatly. I hope I am not sounding like a help vamp. I only ask because my google foo has failed me on where to search for these specific answers. Links are appreciated. I like to do stuff on my own but sometimes the brain cramps. :)
TIA Best, Karl DeSaulniers Design Drumm http://designdrumm.com