The linking table adds more flexibility at the cost of complexity. In this case, I see absolutely no reason for it as it only serves to muck up your data. As Jeff mentioned, a linking table is great for many->many relationships, but otherwise it's just a pain.
Edward Dudlik Becoming Digital www.becomingdigital.com ----- Original Message ----- From: <[EMAIL PROTECTED]> To: "Jeff Shapiro" <[EMAIL PROTECTED]> Cc: "MySQL List" <[EMAIL PROTECTED]> Sent: Friday, 06 June, 2003 03:18 Subject: Re: establishing a relationship Yes, a "linking" table or a "map" table or a "join" table. "Linking" is what I see it called in books I have; yes I understand that. I hope to understand the advice for a third more thoroughly, too. I am doing this for practice so the theory of what I'm being taught is what I'm after and afaik it must be more than the "linking" of many-to-many (busting up a many-to-many as I like to call it. ;) Thanks, more is always welcome. Ted On Friday, June 6, 2003, at 02:31 AM, Jeff Shapiro wrote: > > Ted, > > If in fact you only have a one-to-many relationship, you don't need the > third table (what's also known as a join table in some circles). This > type of table is only really needed if you are doing a many-to-many > (people have 0 to infinity machines, and machines have 0 to infinity > people). > > I fail to see how adding a layer of complexity would help when deleting > or updating records. Unless, of course, you are doing transaction > logging manually. Which might be necessary with some DBMS products, but > I don't think you need to in MySQL because you have the binary and > other logs available. But then, you would need more information in the > third table than just the two primary keys. I wouldn't mind hearing > from your friend about why this type of set up is beneficial. > > jeff > > On Fri, 06 Jun 2003 02:14:37 -0400, [EMAIL PROTECTED] wrote: >> I have a friend teaching me but I want more :-) (second opinions), >> please. >> >> A simple Database: >> 2 tables >> a one-to-many relationship >> each table has a Primary Key: table1 (one) Primary Key = peopleID; >> table2 (many) Primary Key = machinesID >> >> Normally, I would put the peopleID also in table2 as a Foreign key to >> establish the relationship and be done with it. >> >> I am being taught now to create a third table, table3, and in it have >> 2 columns; those being the peopleID and machinesID (the Primary keys >> from the other 2 tables). This is apparently a good idea when it >> comes to deleting or updating records. (?) >> >> My question is, how is the relationship between table1 and table2 >> established using this method? >> >> I hope you understand my question. If I try to explain further it >> will only become convoluted, possibly more than it is! >> >> Thanks, >> Ted Rogers -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
