Stefan Schwarzer schrieb:
Hi there,
I learned in another posting that my table design - in a polite way -
"could be improved".
So, before doing any additional design errors, I would like to get
feedback, if possible.
I am dealing with some 500 tables for worldwide national statistics
(GDP, population, environment etc.), covering approx. 30 years each. For
each of these variables, I usually have as well (pre-prepared)
subregional and regional aggregations too. These could - and should - at
the end be calculated on-the-fly, and not pre-calculated and imported
from Excel as it is for the moment.
My (national) table for a given variable is in the moment as follows (id
being the identifier for a specific country):
id | 1970 | 1971 | ... | 2004 | 2005
-------------------------------------------------------------------
1 | NULL | 36 | ... | 42 | 45
2 ......
The new design would be like this:
id | year | value
-------------------------------
1 | 1970 | NULL
1 | 1971 | 36
1 ....
1 | 2005 | 45
2 | 1970 | ....
2 .....
Would that be considered as "good table design" then?
I'd not save null values but otherwise you are fine.
If you want to select over stable ranges of years
w/o bothering with non existent data (and therefore year)
it might be usefull to have a separate mapping table like
year -> year_id (sequential) and use the Ids for year.
This can even be simplified to a table just providing you the
coverage of years you have as a whole and use the number
directly as foreign key in your table.
table:years
year
1970
1971
1972
...
table:measures
measure_id,description
1 foovar
2 barvar
...
table:values
year (fk from years), measure_id (fk from measures), value
1971 1 36
every column of "values" table would be not null and
primary key (year,measure_id)
This way you can easily create any report you want
by selectiong a year range, then left join the values table
as often as you want for a given measure and so on.
Regards
Tino
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