sql server 2005 - How to get fast result while Querying a very large database table? -

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my client has large database. 2 tables contain patients record having more 10 million rows. when select patient record particular patient record in 2-3 seconds. if pass between date clause in where condition , not records before 25-30 minutes. query-

select convert(varchar(12),[datetime],101) [datetime] , min(cast(response int))     [minfalltotal], max(cast(response int)) [maxfalltotal] nurqueryresults visitid = 'w3074332666' , queryid = 'nurfallz' group convert(varchar(12),[datetime],101)

i result of upper query in 2-3 seconds not this-

select visitid, min(cast(response int)) [minfalltotal], max(cast(response int)) [maxfalltotal] nurqueryresults queryid = 'nurfallz' , convert(varchar(12),[datetime],101)='12/23/2010' group convert(varchar(12),[datetime],101), visitid

actual requirement is-

select top 10 av.visitid [unit], av.accountnumber [account], av.name [patient name], convert(varchar(11),av.birthdatetime,101) [dob] , convert(varchar(12),nq.[datetime],101) [datetime], (cast(min(cast(nq.response int)) varchar(5))+ ' - ' + cast(max(cast(nq.response     int)) varchar(5)) ) [fall] admvisits av join nurqueryresults nq on av.visitid = nq.visitid   nq.queryid = 'nurfallz' , convert(varchar(12),nq.[datetime],101) = '12/24/2010' group convert(varchar(12),nq.[datetime],101), av.visitid, av.accountnumber, av.name, convert(varchar(11),av.birthdatetime,101)

can tell me why taking time execute , solution??

you need examine query plan poorly performing code. paste query in window , hit ctrl+l. should pretty tell doesn't like.

if use ssms 2008 ide connected sql2005 databases , run query plan, t should give recommendation on missing indexes query.

based on limited information provided, without seeing structures, indexes, etc. of tables involved, between query should running in less second in cases..


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