Oracle-L: RE: SQL queries

From: Mark Leith <mark_at_cool-tools.co.uk>
Date: Thu, 14 Mar 2002 03:26:15 -0800
Message-ID: <F001.00428D99.20020314032615@fatcity.com>

Cheers Lee! One up for the "bad guys"! ;P   -----Original Message-----
  From: root_at_fatcity.com [mailto:root_at_fatcity.com]On Behalf Of Robertson Lee - lerobe
  Sent: 12 March 2002 16:24
  To: Multiple recipients of list ORACLE-L   Subject: SQL queries

All,

Following SQL runs for ages (almost 2 hours)

  select * from table1 addr,
  table2 pers,
  table3 lookup
  table4 cust
  where cust.customer_key = lookup_customer_key   and lookup_address_key = addr_address_key   and lookup.person_key = pers.person_key   and rownum < 1000;

when this is changed to

  select /*+ FIRST_ROWS */
  ADDR.*,
  PERS.*,
  LOOKUP.*,
  CUST.*
  from table4 cust,
  table2 pers,
  table3 lookup
  table1 addr
  where cust.customer_key = lookup.customer_key + 0   and lookup.address_key = addr.address_key   and pers.person_key = lookup.person_key + 0   and rownum < 1000;

this runs instantaneously. I realise that 99.99% of the improvement is down to the first_rows hint BUT, why does the SQL tool use the list of table aliases with .* after it AND what on earth are the + 0s' on two lines of the predicate list.

Confused

Lee

PS. The Tool is SQLExpert brought to you by those nice blokes at cool-tools (Cheers Mark Leith !!) and is proving absolutely priceless here at the moment.

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Author: Mark Leith
INET: mark_at_cool-tools.co.uk

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