John, Michael, Andy and James, Thanks for the informative responses. I was hoping I was on the right track. Thanks for the query help, too. It looks like this is going to work just fine.
Cheers, Rik Forgo JIST3 Army Test, Training and Technology Integration Office (T3I) Diverse Technologies Corp. (c) 443.463.8571 (h) 410.859.8474 > -----Original Message----- > From: John Ragan [mailto:jragan@;arkansas.net] > Sent: Thursday, November 07, 2002 10:16 AM > To: [EMAIL PROTECTED]; Richard Forgo > Subject: RE: Newbie: Intersecting entities > > > aha! sure. you weren't being vague. you just > needed to educate me. > > some of us have used intersecting entities > through the years, but didn't know that there was > a fancy name for what we were doing. if my > memory weren't so bad, i'd use it to impress > people in the next interview. > > in this case, simply do a three way multiple join > with the intersecting entity in the middle. > something like this: > select table1.col2, table 3.col2 > from table1 > left join table2 on table1.col1 = table2.col1 > left join table3 on table2.col2 = table3.col1 > > or you could use an equal join with the > intersecting entity in the middle. > > if you have a windows box that you can use as a > front end, i strongly recommend that you download > corereader because its point and click queries > can make a six way join look simple. then, it'll > show you the sql code. best of all is that it's > free. http://corereader.com > > > > > Sorry for being vague. I think the closest thing I can find to it is, > > possibly, a three-way join. I'm trying to figure out how to write the > > query. > > > > I've got the following tables: > > > > systems > > ------------------------ > > sys_name ID > > ------------------------ > > Abrams 202 > > Patriot 544 > > Stinger 229 > > > > ... and ... > > > > new_req > > ------------------------ > > proj_name ID > > ------------------------ > > Test Bed Alpha 344 > > Tracked Wheels 989 > > Battle Monitor 823 > > Shoulder Harness 654 > > Ammo Flask 454 > > Spotter 773 > > > > There may be multiple new requirements for a single system. To > > accommodate them, I created a new table -- an intersecting entity is > > what I recall it being called -- to bridge the two. I can't keep the > > multiple references to new_req in the systems table, nor can I keep them > > in the new_req table. As best I can figure, I need to have a bridge > > table ... e.g., > > > > ie_sys_req > > ------------------------ > > sys_id proj_name_id > > ------------------------ > > 202 344 > > 202 989 > > 202 823 > > 544 654 > > 544 454 > > 544 773 > > > > If this seems peculiar, have patience with me I'm new at this. If it's > > right, let me know so I can breath a sigh of relief. And if the > > structure is right, could someone offer some guidance on how a query > > that allows me to query new_req using the intersecting entity (or > > three-way join, whatever it's called) would be written. > > > > Thanks, > > > > > > Rik Forgo > > JIST3 > > Army Test, Training and Technology Integration Office (T3I) > > Diverse Technologies Corp. > > (c) 443.463.8571 > > (h) 410.859.8474 > > > > > > > -----Original Message----- > > > From: John Ragan [mailto:jragan@;arkansas.net] > > > Sent: Wednesday, November 06, 2002 6:55 PM > > > To: [EMAIL PROTECTED]; Richard Forgo > > > Subject: Re: Newbie: Intersecting entities > > > > > > > > > if a succinct statement is possible, perhaps you > > > could give us an idea of its nature? > > > > > > somebody may be familiar with the concept under a > > > different name. > > > > > > > > > > I'm trying to find some documentation on creating intersecting > > entities > > > > in MySQL, but haven't been able to track any info down on the MySQL > > site > > > > or on the web. At least we called them intersecting entities while > > I > > > > was in Oracle training (which was some time ago). I think I > > remember > > > > how to set them up, but I'd love to have something to refer to > > quickly > > > > before I start. Can anyone point me in the right direction? > > > > > > > > > > > > Rik Forgo > > > > JIST3 > > > > Army Test, Training and Technology Integration Office (T3I) > > > > Diverse Technologies Corp. > > > > (c) 443.463.8571 > > > > (h) 410.859.8474 > > > > > > > > > > > > > > > > > > > > > > > > -- > > > John Ragan > > > [EMAIL PROTECTED] > > > http://www.CoreReader.com/ > > > > > > > > > --------------------------------------------------------------------- > > > Before posting, please check: > > > http://www.mysql.com/manual.php (the manual) > > > http://lists.mysql.com/ (the list archive) > > > > > > To request this thread, e-mail <[EMAIL PROTECTED]> > > > To unsubscribe, e-mail <mysql-unsubscribe- > > > [EMAIL PROTECTED]> > > > Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > > > > > > > > > > -- > John Ragan > [EMAIL PROTECTED] > http://www.CoreReader.com/ > > > --------------------------------------------------------------------- > Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > > To request this thread, e-mail <[EMAIL PROTECTED]> > To unsubscribe, e-mail <mysql-unsubscribe- > [EMAIL PROTECTED]> > Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
