Re: count(*) ?
Date: Wed, 16 Jan 2008 09:33:19 +0100
"Frank van Bortel" <frank.van.bortel_at_gmail.com> schreef in bericht
> 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?
> Test it - it is not so - who do you believe?!?
> 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 Received on Wed Jan 16 2008 - 02:33:19 CST