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Home > Archive > MS SQL Server OLAP > September 2005 > Multiple joins to the same underlying table
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Multiple joins to the same underlying table
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| I have a cube which has 7 different time dimensions. For each time dimension
I have created a separate view: e.g. vwTime1, vwTime2, vwTime3, etc...
In my fact table I have Date1, Date2, Date3, etc... which join to their
respective Time views. This cube is taking a VERY Long time to process and
I've tracked down the problem to the 7 joins from the fact table to the Time
table based on the results from running an "Estimated Execution Plan" in
Query Analyzer. Does anyone have any advice on how to optimize or reduce the
number of joins to the time table?
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| Jéjé 2005-09-10, 1:23 pm |
| have try to optimize your cube?
otimizing a cube remove some joins , but you have to make sure that all the
date1,2,3... exists in each dimension.
the join used by default is here to insure that the loaded fact table
contains only known dimension member.
before optimizing your cube, you have to insure that the lowest level of the
dimension is unique (member key must be unique)
you can optimize manually by changing the column used at the lowest level of
the dimension in the cube. change the column used from the vwTime1 table to
the fact.date1 column. this step remove the join because you no longer need
it. (the opitmize cube do this for you automatically)
"Matt" <Matt@discussions.microsoft.com> wrote in message
news:4615B8EE-1EFE-4E2B-A523- 2A0ABB8BF480@microso
ft.com...
>I have a cube which has 7 different time dimensions. For each time
>dimension
> I have created a separate view: e.g. vwTime1, vwTime2, vwTime3, etc...
>
> In my fact table I have Date1, Date2, Date3, etc... which join to their
> respective Time views. This cube is taking a VERY Long time to process
> and
> I've tracked down the problem to the 7 joins from the fact table to the
> Time
> table based on the results from running an "Estimated Execution Plan" in
> Query Analyzer. Does anyone have any advice on how to optimize or reduce
> the
> number of joins to the time table?
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| Rolando Matarrita 2005-09-20, 11:23 am |
| You can also create a hierarchy for all the time dimensions, so that they
share their aggregations
Rolando
"Jéjé" < willgart@AAAhotmailB
BB.com> wrote in message
news:eDppmcitFHA.3720@TK2MSFTNGP14.phx.gbl...
> have try to optimize your cube?
> otimizing a cube remove some joins , but you have to make sure that all
the
> date1,2,3... exists in each dimension.
> the join used by default is here to insure that the loaded fact table
> contains only known dimension member.
>
> before optimizing your cube, you have to insure that the lowest level of
the
> dimension is unique (member key must be unique)
>
> you can optimize manually by changing the column used at the lowest level
of
> the dimension in the cube. change the column used from the vwTime1 table
to
> the fact.date1 column. this step remove the join because you no longer
need
> it. (the opitmize cube do this for you automatically)
>
>
> "Matt" <Matt@discussions.microsoft.com> wrote in message
> news:4615B8EE-1EFE-4E2B-A523- 2A0ABB8BF480@microso
ft.com...
reduce[color=darkred
]
>
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