Ales Zoulek wrote:
Hi,
I've read reacently, that it's not good to use columns with NULL
values in MySQL, because it slows down the select queries over that
columns. Is it true? Or do that affects only some situations or some
versions? Are there some relevant statistics about that?
There is not really a noticeable slowdown just for having NULLable
columns. However, there are situations where separating off frequently
accessed columns from (often NULLable) infrequently accessed columns
into two or more tables can provide very good performance improvement,
as the infrequently accessed columns have much less likelihood from
taking up space in memory, especially in memory-starved applications.
Cheers,
Jay
On 3/29/07, Reinhart Viane <[EMAIL PROTECTED]> wrote:
Hello list,
I have a table events in a database that has a field named duration. This
field is a mediumint containing an amount of minutes (eg 65, 87, 10368)
Now I need these to be outputted into a h:mm (so 65 will be
represented as
1:05)
My complete query is:
select YEAR(events.workdate) as theyear,
(sum(events.duration)/60),clients.name, persons.name from events,
persons,
clients where events.personid= persons.personid and events.clientid=
clients.clientid group by clients.name, events.personid, theyear;
this does, off course not give me the wanted result.
How can I convert these numerical entries to hh:mm in my query?
(days do not matter, I just need hours and minutes, thx)
Regards and thanks,
Reinhart Viane
D-studio
Graaf van Egmontstraat 15/3
2800 Mechelen
[EMAIL PROTECTED] +32(0)15 44 89 01
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