Since the primary key/foregin key can be composite, there can be more than n-1 join conditions, but there will be only n-1 joins.
e.g. A's primary key is col1 and col2 referred by B's col1 and col2 in this case you will only have 1 join, between A and B, but 2 join conditions A.col1 = B.col1 and A.col2 = B.col2 but in no case you should join A to B, B to C and then A to C again. If you need to do that, then go one step back and look at the design. Regards Naveen -----Original Message----- Sent: Thursday, February 27, 2003 11:36 PM To: Multiple recipients of list ORACLE-L If you are joining 'n' number of tables, you should have a minimum of 'n-1' joining conditions, otherwise it might result in cartesian product. Sunil Nookala Dell Corp. -----Original Message----- Sent: Thursday, February 27, 2003 10:29 AM To: Multiple recipients of list ORACLE-L 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. 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