<SARCASM>
And if you fail to follow Dan's advice, and that one of the tables in the FROM clause is just used to link two other tables or perform an existence test (not to return data in the select list), just do like everybody else :
add DISTINCT
</SARCASM>
>----- ------- Original Message ------- -----
>From: "Daniel W. Fink" <optimaldba_at_yahoo.com>
>To: Multiple recipients of list ORACLE-L
><ORACLE-L_at_fatcity.com>
>Sent: Thu, 27 Feb 2003 08:19:59
>
>The minimum number of equi-joins (a = a) is the
>number of tables - 1.
>For 3 tables, a minimum of 2 join conditions are
>needed. Additional
>joins are needed for composite values (relationship
>defined by multiple
>columns) or theta joins (where the join is on a
>range of values).
>
>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
>>
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Stephane Faroult
INET: sfaroult_at_oriolecorp.com
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: ListGuru_at_fatcity.com (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).
Received on Thu Feb 27 2003 - 11:09:37 CST
