Re: newbie question

ivan marchesini <marchesini(at)unipg(dot)it> schrieb:

> Dear users..
> I have fastly created a table in a postgresql database..
> some columns where edited by hand (columns A, B, C), and some others
> (columns D, E, F) have been calculated as a result of mathematical
> equation (where the factors are the A, B, C columns)....

You should create a table with (a,b,c) and a view. Below a example.

test=# create table foo (a int, b int, c int);
CREATE TABLE

test=# create view foo_view as (select a,b,c,a*b as ab, a*c as ac, b*c as bc from foo);
CREATE VIEW

> now I simply need to change some values in the A, B, C columns and I
> would like to obtain the correct values in the D, E, F column...
> I know that this is a tipical problem of a spreadsheet but how can I
> solve it with a DBMS??

test=# insert into foo values (2,3,4);
INSERT 0 1
test=# select * from foo_view ;
a | b | c | ab | ac | bc
---+---+---+----+----+----
2 | 3 | 4 | 6 | 8 | 12
(1 row)

test=# update foo set a=3;
UPDATE 1
test=# select * from foo_view ;
a | b | c | ab | ac | bc
---+---+---+----+----+----
3 | 3 | 4 | 9 | 12 | 12
(1 row)

HTH, Andreas
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