mysql - What is the effect of performance of a SQL query when have aggregate function and where clause -


i have 2 queries :

1. 

select u.unitid unitid,          u.unitscode 'unitscode',          ( cast(count(vd.date) float) / u.timediff ) * 100 'bookingcount',          u.tradestarttime,          u.tradestoptime,          u.minimumslot,          u.maximumterm     @alldates vd          inner join commcmlbookingdetail cd                  on vd.date between cd.dtfromtime , cd.dttotime                     , datepart(minute, vd.date) = datepart(minute, cd.dtfromtime)          inner join commcmlbooking cb                  on cb.hmy = cd.hbooking                     , cb.istatus = 1                     , cb.itype = 525          inner join @unitsinfo u                  on u.unitid = cb.hunit                     , cast(vd.date date) between cast(@bookingfromdate date) , cast(@bookingtodate date)                     , cast(vd.date time) between cast(u.tradestarttime time) , cast(u.tradestoptime time)    cb.hrecord = case when @amendmentid = 0 cb.hrecord else @amendmentid end    group  u.unitid,             u.unitscode,             u.minimumslot,             u.tradestarttime,             u.timediff,             u.tradestoptime,             u.maximumterm;

2. 

insert @tempbookingcount       select u.unitid,              u.timediff         @alldates vd              inner join commcmlbookingdetail cd                      on vd.date between cd.dtfromtime , cd.dttotime                         , datepart(minute, vd.date) = datepart(minute, cd.dtfromtime)              inner join commcmlbooking cb                      on cb.hmy = cd.hbooking                         , cb.istatus = 1                         , cb.itype = 525              inner join @unitsinfo u                      on u.unitid = cb.hunit                         , cast(vd.date date) between cast(@bookingfromdate date) , cast(@bookingtodate date)                         , cast(vd.date time) between cast(u.tradestarttime time) , cast(u.tradestoptime time)        cb.hrecord = case when @amendmentid = 0 cb.hrecord else @amendmentid end    insert @unitbookingcount   select tt.unitid,          u.unitscode,          ( cast(count(tt.unitid) float) / tt.timediff ) * 100,          u.tradestarttime,          u.tradestoptime,          u.minimumslot,          u.maximumterm     @tempbookingcount tt          inner join @unitsinfo u                  on u.unitid = tt.unitid   group  tt.unitid,             tt.timediff,             u.tradestarttime,             u.tradestoptime,             u.minimumslot,             u.maximumterm,             u.unitscode

i have separated first query 2 parts, , can huge difference in performance!
first query take 14 seconds when executed 5 months next query take 4 seconds.

your original query uses 2 table variables @alldates , @unitsinfo.

by using table variables, aren't giving sql fighting chance of optimizing query because there no statistics on table variables , row count estimations , query plan impacted.

one reference, can find many more: http://blogs.msdn.com/b/psssql/archive/2010/08/24/query-performance-and-table-variables.aspx

try original #temptables instead of @tablevars


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