Two! PK on stn_rstcn_to_frm?
T'would be clearer if you presented your problem as tables a, b, c, rather than getting us to struggle through all these stns... peter -----Original Message----- [mailto:[EMAIL PROTECTED] Sent: 27 February 2003 14:59 To: Multiple recipients of list ORACLE-L Dear List, I have a basic doubt about the number of joins I should have. Say, I have three tables by name station, station_restriction and stn_rstcn_to_frm with the following structure: Station Station_restriction stn_rstcn_to_frm ---------- ---------------------------- ------------------------- stn_key(PK) stn_rstcn_key(PK) stn_rstcn_key(FK) station_code stn_key(FK) stn_key(FK) station_name restricted_position country If I have to select data from all the three tables should I have two joins or three joins? If I have two joins, I would have Station.stn_key=Station_restriction.stn_key and Station_restriction.stn_rstcn_key = stn_rstcn_to_frm.stn_rstcn_key. If I have three joins I would have Station.stn_key=Station_restriction.stn_key and Station_restriction.stn_rstcn_key = stn_rstcn_to_frm.stn_rstcn_key and Station.stn_key = stn_rstcn_to_frm.stn_key Can anybody let me know as to how many joins should I have so that I don't get any cartesian product in the result set? I am sorry if the question sounds trivial to someone but I got this basic doubt while writing a complex query for a multi-table join. Any help in this regard is very much appreciated. Thanks and Regards, Ranganath WARNING: The information in this message is confidential and may be legally privileged. It is intended solely for the addressee. Access to this message by anyone else is unauthorised. If you are not the intended recipient, any disclosure, copying, or distribution of the message, or any action or omission taken by you in reliance on it, is prohibited and may be unlawful. Please immediately contact the sender if you have received this message in error. Thank you. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Krishnaswamy, Ranganath INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). ********************************************************************* This e-mail message, and any files transmitted with it, are confidential and intended solely for the use of the addressee. If this message was not addressed to you, you have received it in error and any copying, distribution or other use of any part of it is strictly prohibited. Any views or opinions presented are solely those of the sender and do not necessarily represent those of the British Geological Survey. The security of e-mail communication cannot be guaranteed and the BGS accepts no liability for claims arising as a result of the use of this medium to transmit messages from or to the BGS. The BGS cannot accept any responsibility for viruses, so please scan all attachments. http://www.bgs.ac.uk ********************************************************************* -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Robson, Peter INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
