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Using Joins slow down query execution
Posted: 02 September 2009 06:15 AM   Ignore ]  
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Total Posts:  43
Joined  2009-08-11

Hello,
I found strange thing.
when I execute query with join, I receive result after 58 seconds, if I don’t use joins execution time is 2 sec.

select   a11.field_1_id field_1_id,
  max(a12.field_1_name)  field_1_name,
  a11.field_2_id field_2_id,
  max(a13.field_2_name)  field_2_name,
  a11.field_3_id field_3_id,
  max(a14.field_3_name)  field_3_name,
  a11.job_id job_id,
  a11.loan_id loan_id,
  a11.field_4_id field_4_id,
  max(a15.field_4_name)  field_4_name,
  sum(a11.column1)  WJXBFS1,
  sum(a11.column2)  WJXBFS2,
  sum(a11.column3)  WJXBFS3,
  sum(a11.column4)  WJXBFS4,
  sum(a11.column5)  WJXBFS5
from   my_table   a11
  join   field_1   a12
    on   (a11.field_1_id = a12.field_1_id)
  join   field_2   a13
    on   (a11.field_2_id = a13.field_2_id)
  join   field_3   a14
    on   (a11.field_3_id = a14.field_3_id)
  join   field_4   a15
    on   (a11.field_4_id = a15.field_4_id)
where   (a11.job_id = 1
or a11.job_id = 2)
group by   a11.field_1_id,
  a11.field_2_id,
  a11.field_3_id,
  a11.job_id,
  a11.loan_id,
  a11.field_4_id;

——————- 58 seconds—————-

select   a11.field_1_id field_1_id,

  a11.field_2_id field_2_id,

  a11.field_3_id field_3_id,

  a11.job_id job_id,
  a11.loan_id loan_id,
  a11.field_4_id field_4_id,

  sum(a11.column1)  WJXBFS1,
  sum(a11.column2)  WJXBFS2,
  sum(a11.column3)  WJXBFS3,
  sum(a11.column4)  WJXBFS4,
  sum(a11.column5)  WJXBFS5
from   my_table   a11
where   (a11.job_id = 1
or a11.job_id = 2)
group by   a11.field_1_id,
  a11.field_2_id,
    a11.field_3_id,
  a11.job_id,
  a11.loan_id,
  a11.field_4_id;
———2 seconds———

In both cases result set is 300 K records.

Could you please explain why first query took long time execution?
Thanks,
Alexander.

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Posted: 02 September 2009 07:47 AM   Ignore ]   [ # 1 ]  
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This is a duplicate of http://www.infobright.org/Forums/viewthread/1053/

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