Krishnaswamy, Ranganath wrote:
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
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