Re: count(*) ?
From: shakespeare <whatsin_at_xs4all.nl>
Date: Thu, 17 Jan 2008 13:45:01 +0100
Message-ID: <478f4dcc$0$85792$e4fe514c@news.xs4all.nl>
>>> shakespeare wrote:
>>> No I was not confused, though have to admit I misread the
>>> column name bit.
>>> The title had the start of another count(1) (or count(42),
>>> for that matter) is better (or worse) that count(*).
>>> That myth I wanted to stop right here.
>>> As far as the count(col) vs count(*) myth:
>>> http://www.oracledba.co.uk/tips/count_speed.htm
>>> Of course, assuming you want to know how many
>>> entries your table has (so not hanky-panky with
>>> nullable columns!)
>>> --
>>> Regards,
>>> Frank van Bortel
>>> Top-posting in UseNet newsgroups is one way to shut me up
Date: Thu, 17 Jan 2008 13:45:01 +0100
Message-ID: <478f4dcc$0$85792$e4fe514c@news.xs4all.nl>
I agree....
Shakespeare
"Frank van Bortel" <frank.van.bortel_at_gmail.com> schreef in bericht news:ee2e3$478f3600$524b5c40$17910_at_cache2.tilbu1.nb.home.nl...
> shakespeare wrote: >> "Frank van Bortel" <frank.van.bortel_at_gmail.com> schreef in bericht >> news:ee096$478f27b0$524b5c40$17089_at_cache3.tilbu1.nb.home.nl...
>>> shakespeare wrote:
>>>> "Frank van Bortel" <frank.van.bortel_at_gmail.com> schreef in bericht >>>> news:7767f$478cff47$524b5c40$12171_at_cache5.tilbu1.nb.home.nl... >>>>> nick wrote: >>>>>> I understand that when you feed the count( ) function an asterisk as >>>>>> an argument it runs >>>>>> slower than if you use a column name as an argument. Can someone tell >>>>>> me why this is so? >>>>>> >>>>>> Thanks >>>>> Test it - it is not so - who do you believe?!? >>>>> >>>>> -- >>>>> >>>>> Regards, >>>>> Frank van Bortel >>>>> >>>>> Top-posting in UseNet newsgroups is one way to shut me up >>>> O yes it is! If you have a sparse column (say col_a), indexed in a very >>>> large table, count(col_a) will use the index , where count(*) doesn't >>>> (and >>>> they will return different values as well). >>>> I think you confused this with select (*) and select (1) (which perform >>>> the >>>> same, although you might find a DBA at your current working place who >>>> is >>>> convinced that count (8) is faster.....). They ARE not the same though, >>>> for >>>> count(*) from table in a view will not invalidate a view when a column >>>> is >>>> added to the table, where count(1) will..... >>>> >>>> Shakespeare >>>> >>>>
>>> No I was not confused, though have to admit I misread the
>>> column name bit.
>>> The title had the start of another count(1) (or count(42),
>>> for that matter) is better (or worse) that count(*).
>>>
>>> That myth I wanted to stop right here.
>>>
>>> As far as the count(col) vs count(*) myth:
>>> http://www.oracledba.co.uk/tips/count_speed.htm
>>>
>>> Of course, assuming you want to know how many
>>> entries your table has (so not hanky-panky with
>>> nullable columns!)
>>> --
>>>
>>> Regards,
>>> Frank van Bortel
>>>
>>> Top-posting in UseNet newsgroups is one way to shut me up
>> >> Sorry, that's what I meant too, but I wrote "select" where I should have >> written "count". >> And about hanky panky: it's nullable columns that make the difference in >> count(column) and count(*) (different speed, different results). >> The "myth" article is about count(1), count(*) and count (rowid) and >> things >> like that. >> >> Shakespeare >> >> Shakespeare >> >> > As well as Primary Key columns - bottom line: > it does not matter. > http://asktom.oracle.com/pls/asktom/f?p=100:11:3615348475281792::::P11_QUESTION_ID:1156159920245 > -- > > Regards, > Frank van Bortel > > Top-posting in UseNet newsgroups is one way to shut me upReceived on Thu Jan 17 2008 - 06:45:01 CST