How Large Is Too Large?

Hi,
Just got done with the requirements gathering and discovered
that my users want to measure about 200 items with the warehouse. So
I envision a Fact table with about 200 columns. This seems quite
large to me - but maybe other developers feel differently.
So my question is this: Is a data warehouse that contains a
single Fact table with 200 columns realistic and feasible? Or is a
single table with 200 columns a bad way to go?
JDI don't think actual number of columns in the table could be used as metric
for good or bad design. Number of columns depends on object/data model you
choose.
If object requires 1000 measurements, all 1000 must be implemented. If all
of them can't fit into single row, then you will use 2 or more tables. But
in any case you will implement all required measurements
HTH
Alex
"Joe" <delphi561@.cox.net> wrote in message
news:1181227222.752767.93740@.o11g2000prd.googlegroups.com...
> Hi,
> Just got done with the requirements gathering and discovered
> that my users want to measure about 200 items with the warehouse. So
> I envision a Fact table with about 200 columns. This seems quite
> large to me - but maybe other developers feel differently.
> So my question is this: Is a data warehouse that contains a
> single Fact table with 200 columns realistic and feasible? Or is a
> single table with 200 columns a bad way to go?
>
> JD
>|||200 is not above the limit for columns, but may be > ~8K bytes and thus lead
to row overflows and significantly reduced performance. I think it will be
all about what kind of hardware you put the system on. You may be able to
have multiple facts as well.
TheSQLGuru
President
Indicium Resources, Inc.
"Joe" <delphi561@.cox.net> wrote in message
news:1181227222.752767.93740@.o11g2000prd.googlegroups.com...
> Hi,
> Just got done with the requirements gathering and discovered
> that my users want to measure about 200 items with the warehouse. So
> I envision a Fact table with about 200 columns. This seems quite
> large to me - but maybe other developers feel differently.
> So my question is this: Is a data warehouse that contains a
> single Fact table with 200 columns realistic and feasible? Or is a
> single table with 200 columns a bad way to go?
>
> JD
>|||Hello Joe,
In a DW structure I usually see Dimension tables with this number of columns
not fact tables. That said it is not INXS of column counts allowed and if
the number of columns is justifiable then so be it.
Watch out for width though. A fact table should be quite thin not least
because it could be carrying millions upon millions of rows.
Allan Mitchell
http://wiki.sqlis.com | http://www.sqlis.com | http://www.sqldts.com |
http://www.konesans.com

> Hi,
> Just got done with the requirements gathering and discovered
> that my users want to measure about 200 items with the warehouse. So
> I envision a Fact table with about 200 columns. This seems quite
> large to me - but maybe other developers feel differently.
> So my question is this: Is a data warehouse that contains a
> single Fact table with 200 columns realistic and feasible? Or is a
> single table with 200 columns a bad way to go?
> JD
>|||On Jun 12, 9:30 pm, Allan Mitchell <a...@.no-spam.sqldts.com> wrote:
> Hello Joe,
> In a DW structure I usually see Dimension tables with this number of colum
ns
> not fact tables. That said it is not INXS of column counts allowed and if
> the number of columns is justifiable then so be it.
> Watch out for width though. A fact table should be quite thin not least
> because it could be carrying millions upon millions of rows.
> --
> Allan Mitchellhttp://wiki.sqlis.com|http://www.sqlis.com|http://www.sqldts.com|ttp://www.konesans.com" target="_blank">h
ttp://www.konesans.com
>
>
>
>
>
> - Show quoted text -
Very interesting topic.
I guess the end-product is important here.
How will the end-user access the datawarehouse, via T-SQL based
Reports or via a cube or cubes ?
Will the facts be inserts only or will their be updates ?
Are all the facts related and can you easily guess which facts will be
reported on together ?