Oracle-L: Foreign key indexes on individual columns or multiple columns

From: Krishnaswamy, Ranganath <Ranganath.Krishnaswamy_at_blr.hpsglobal.com>
Date: Tue, 14 Jan 2003 02:29:15 -0800
Message-ID: <F001.0052EDAC.20030114022915@fatcity.com>

Hi List,

I have a table by name Benchmark_hdr with the following columns:

  BENCHMARK_HDR_ID    NUMBER        NOT NULL 
  CALENDAR_TYPE     CHAR (1), 
  UOM               VARCHAR2 (10), 
  CALENDAR_PORT     CHAR (1), 
  CUSTOMER_MOT_ID   NUMBER        NOT NULL 
  RESP_PARTY_NAME   VARCHAR2 (10), 
  FROM_EVENT        NUMBER, 
  TO_EVENT          NUMBER, 
  LAST_UPDATED      DATE

I have created foreign key constraints using the below commands:

  ALTER TABLE BENCHMARK_HDR ADD CONSTRAINT BENCHAMRK_HDR_CUSTOMERESP_FK FOREIGN KEY (RESP_PARTY_NAME, CUSTOMER_MOT_ID)   REFERENCES XM.CUSTOMER_RESPONSIBLE_PARTY (RESP_PARTY_NAME, CUSTOMER_MOT_ID) ; ALTER TABLE BENCHMARK_HDR ADD CONSTRAINT BENCHAMRK_HDR_CUSTOMEREVENT_FK FOREIGN KEY (FROM_EVENT)
  REFERENCES XM.CUSTOMER_EVENT (CUSTOMER_EVENT_ID) ON DELETE CASCADE; ALTER TABLE BENCHMARK_HDR ADD CONSTRAINT BENCHMARK_HDR_CUSTOMEREVENT_FK FOREIGN KEY (TO_EVENT)
  REFERENCES XM.CUSTOMER_EVENT (CUSTOMER_EVENT_ID) ON DELETE CASCADE;   The foreign keys need to be indexed so that the child table is not locked when a record in the parent table is being updated or deleted. If the foreign keys are indexed the corresponding child record or records are only locked when the parent table record is being updated or deleted. In this context I would like to seek the advice of the list as to whether I should create indexes on individual foreign keys or should I create one or more composite index(es) on foreign keys? If I need to create a composite index on which columns should I base my index on? Could anybody advise me on this with the reasons for following that particular approach? Any help in this regard is very much appreciated.

Thanks and Regards,

Ranganath

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Author: Krishnaswamy, Ranganath
INET: Ranganath.Krishnaswamy_at_blr.hpsglobal.com

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