sql server - SQL slow subquery -

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i trying retrieve data large audits table (millions of rows). need make query run efficiently possible. first playing subquery return objecttypeid , use limit query on audit table

this query taking 4 minutes run:

select distinct audits.objecttypeid,  count(*) count audits audits audits.objecttypeid =  (select distinct objecttype.objecttypeid objecttype objectname = 'data') group audits.objecttypeid

if default in objecttypeid query runs in 42 seconds

select distinct(audits.objecttypeid), count(*) count audits  audits.objecttypeid = 1 group audits.objecttypeid

but subquery when run in isolation takes second run. why should first query take long?

i can see 3 things might help:

  1. pull objecttypeid variable: since there should 1 value it
  2. take out distinct on both queries since should unnecessary (the subquery should have 1 value , grouping value in outer query
  3. take out group since querying 1 objecttypeid

so final query be:

declare @objecttypeid int  select @objecttypeid = (select objecttype.objecttypeid                          objecttype                          objectname = 'data')  select audits.objecttypeid,  count(*) count audits audits audits.objecttypeid = @objecttypeid

if executing single statement , not batch or stored procedure (meaning can't use variables) thne can keep subquery:

select audits.objecttypeid,  count(*) count audits audits audits.objecttypeid =      (select objecttype.objecttypeid       objecttype       objectname = 'data')

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