Re: Is it possible to use a field from another table as part of a query?

Partick,

> I have a table that contains a VARCHAR field with data formatted as such:
> 12,44,13,225
> what I would like to do is use this field in a query to another table such
> as:

1. Since you are a smart guy, I'm assuming that this "delimited" VARCHAR data
is legacy data that you don't have a choice about re-structuring. Because,
of course, the normalized way to store the data would be in a subtable, not a
VARCHAR field.

>
> CREATE TABLE category_tree (
> tree varchar(200)
> ) WITH OIDS;
>
> Select * from mdc_products
> where keyf_category_home IN (select tree from category_tree)
>
> However, my keyf_category_home field is an INT4. Is there a way to parse
> out the tree field so that I can define it as INT4?

Well, this is easiest thing to do:

Select * from mdc_products
where EXISTS
(select tree from category_tree
WHERE tree ~ ('(^|,)' || keyf_category_home || '(,|$)'));

(somebody please correct my regexp if I've made an error)

... but that's impossible to index. If the table category_tree doesn't
change often, I'd write a program to parse the data and build a normalized
subtable containg a vertical colum of tree values.

--
-Josh Berkus
Aglio Database Solutions
San Francisco