??? how to interpret query plan

From: Janet Linsy <janetlinsy_at_yahoo.com>
Date: Fri, 11 May 2001 14:49:09 -0700
Message-ID: <F001.003019BD.20010511145539@fatcity.com>

Hi all,

I know how to generate the query plan but how to interplate the query plan, really? The only thing I know is if there is a FULL TABLE SCAN, that most probably is bad, need to build an index. However, if the query plan shows me something else, I don't know what to improve.

For example, does the following look good??? (this is just one example, please throw me any idad you can think of. Thank you!)

Query Plan

---

SELECT STATEMENT cost=
  NESTED LOOPS OUTER
    NESTED LOOPS OUTER

      NESTED LOOPS OUTER
        NESTED LOOPS OUTER
          TABLE ACCESS BY INDEX ROWID
CUSTOMER_ACCOUNT_CONTACTS
            INDEX RANGE SCAN
CUSTOMER_ACCOUNT_CONTACTS_1
          TABLE ACCESS BY INDEX ROWID PHONE
            INDEX UNIQUE SCAN PK_PHONE
        TABLE ACCESS BY INDEX ROWID PHONE
          INDEX UNIQUE SCAN PK_PHONE
      TABLE ACCESS BY INDEX ROWID PHONE
        INDEX UNIQUE SCAN PK_PHONE
    TABLE ACCESS BY INDEX ROWID PHONE
      INDEX UNIQUE SCAN PK_PHONE

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Author: Janet Linsy
  INET: janetlinsy_at_yahoo.com

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