RE: What does LIKE '%%' actually do in a WHERE clause?
- From: "Dunbar, Norman (Capgemini)" <norman.dunbar.capgemini@xxxxxxxxxxxxxxxxxxxxxxxxx>
- To: Subodh Deshpande <deshpande.subodh@xxxxxxxxx>
- Date: Wed, 5 Oct 2011 15:25:04 +0000
Hi Subodh,
>> and if we are going to use rownum then it will be always
>> faster I suppose..
Both queries used the rownum < 101 to just get the first 100 rows.
The one with % in the WHERE clause (and the one with nothing except the joins
between tables) takes over 7 minutes - it has huge cardinalities and I'm sure
that it's joining all 4 tables and then returning the first 100 rows.
The one with %% joins the tables and bungs back the same 100 rows in a couple
of seconds.
<SNIP>
>> not very sure randomly guess may be '%%' will ignore nulls..
Yes, % won't match nulls.
Thanks.
Cheers,
Norm.
Norman Dunbar
Contract Senior Oracle DBA
Capgemini Database Build Team
Internal : 7 28 2051
External : 0113 231 2051
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