Re: Dynamic table with variable number of columns

[Thomas Burdairon <tburdairon@xxxxxxxxxxxxxx>]

if i understand well you need to have an history for your products.

i would have a table B with

date           products            price

1/1/2006     prod1                 1.0

1/1/2006     prod2                 3.0

or replace prod_name py product_id, ...

Thomas

On Jul 12, 2006, at 16:08, nkunkov@xxxxxxxxxxxxx wrote:

Bruno Wolff III wrote:

On Tue, Jul 11, 2006 at 06:05:18 -0700,

  nkunkov@xxxxxxxxxxxxx wrote:

Hello,

I'm a pgsql novice and here is what I'm trying to do:

1.    I need to create a dynamic table with the column names fetched

from the database using a select statement from some other table.  Is

it possible?  Could you point me to a simple example on how to do it?

2.   I would like to compare the list of coulmn names which are values

fetched from some table with the column names of the existing table.

If one of the names doesn't exist as a column name of my table, I'd

like to dynamically alter the table and add a coulmn with the name just

fetched from the DB.

Your help is greatly appreciated.

Thanks

NK

Information on the column names of tables in the database are available

from the information schema and the catlog tables. You can find more about this

in the documentation:

http://www.postgresql.org/docs/8.1/static/information-schema.html

http://www.postgresql.org/docs/8.1/static/catalogs.html

You might get better help by describing the actual problem you are trying to

solve rather than asking for help with a particular approach to solving that

problem. The approach you are trying seems to be seriously broken and it

would probably be a good idea to consider other approaches.

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Thank you for the suggestions.

I will try to describe the problem better.

I have two problems to solve.  First one is that I have to transpose a

table.

I have table A that looks like this:

date          product  price description

1/1/2006   prod1      1.00  some product

1/1/2006   prod2      3.00  other product

I need to transpose this table to create table B

date         prod1    prod2

1/1/2006   1.00      3.00

I think I can use EXECUTE statement and build the table dynamically by

using the result of the select statement for column names. Would that

be the right approach?  Are there good examples somewhere on how to

implement this?

My second problem, is that after creating the above transposed table, I

will be inserting more rows to it from table A and i might have more

products too.  That means I will have to compare the value of product

from table A with the column names of table B and alter the table

accordingly.  To compare coulmn names with the value of product in

table A I think I can use pg_attribute function.  Would that be a right

way to go?

Thanks for your help.

NK

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