So Jay, What benefit do we get if we only null columns in a separate table, since they are null, then there is not point in access this table.
Please correct me , i am bit confused by this. regards anandkl On 3/30/07, Ales Zoulek <[EMAIL PROTECTED]> wrote:
Thanks a lot. I agree with you in meaningful separating columns into tables as you descibed it. I had just impression, that mysql have some inner algoritmic issue with dealing with NULL values. Rgrds. Ales On 3/29/07, Jay Pipes <[EMAIL PROTECTED]> wrote: > 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 > >> > >> > >> > >> -- > >> MySQL General Mailing List > >> For list archives: http://lists.mysql.com/mysql > >> To unsubscribe: > >> http://lists.mysql.com/[EMAIL PROTECTED] > >> > >> > > > > > > -- ------------------------------------------------------ Ales Zoulek NetCentrum s.r.o. +420 739 542 789 +420 604 332 515 ICQ: 82647256 ------------------------------------------------------ -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
