Re: [GENERAL] how to create a new composite type using already existing composite types

[Merlin Moncure]

On Sat, Feb 13, 2010 at 7:24 PM, Jeff Davis pg...@j-davis.com wrote:
 On Wed, 2010-02-10 at 03:46 +, Iain Barnett wrote:

 CREATE TYPE inventory_item2 AS (
     name            text,
     supplier_id     integer,
     price           numeric,
 size  integer
 );


 but it would be handy if I could reuse inventory_item instead of
 having to retype the whole lot. I can't work out or find the right
 syntax, can anyone show me how? Any help would be much appreciated.

 What about:

  CREATE TYPE inventory_item2 AS (
    ii inventory_item,
    size integer
  );

 or:

  CREATE TABLE inventory_item2 (
    LIKE inventory_item,
    size integer
  );

Pretty neat.  I wasn't aware you could mix LIKE with explicit field
declarations.

Those expressions produce different results...the first creates a type
within a type (nested) and the second creates a new unnested type
based on the fields of the original type.  The first expression
creates a dependency while the second does not.  This flexibility is
only possible if you create types with the 'create table' statement.

merlin

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Re: [GENERAL] how to create a new composite type using already existing composite types

[Jeff Davis]

On Wed, 2010-02-10 at 03:46 +, Iain Barnett wrote:

 CREATE TYPE inventory_item2 AS (
 nametext,
 supplier_id integer,
 price   numeric,
 size  integer
 );
 
 
 but it would be handy if I could reuse inventory_item instead of
 having to retype the whole lot. I can't work out or find the right
 syntax, can anyone show me how? Any help would be much appreciated.

What about:

  CREATE TYPE inventory_item2 AS (
ii inventory_item,
size integer
  );

or:

  CREATE TABLE inventory_item2 (
LIKE inventory_item,
size integer
  );

and that will automatically create the type.

Regards,
Jeff Davis



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[GENERAL] how to create a new composite type using already existing composite types

[Iain Barnett]

Hi,

Is there a way to create a new composite type using already existing composite 
type?

For example,

CREATE TABLE inventory_item (
nametext,
supplier_id integer REFERENCES suppliers,
price   numeric CHECK (price  0)
);

produces the following type automatically
CREATE TYPE inventory_item AS (
nametext,
supplier_id integer,
price   numeric
);

but I'd also like to have a type with an extra column for certain functions

CREATE TYPE inventory_item2 AS (
nametext,
supplier_id integer,
price   numeric,
sizeinteger
);

but it would be handy if I could reuse inventory_item instead of having to 
retype the whole lot. I can't work out or find the right syntax, can anyone 
show me how? Any help would be much appreciated.

Regards
Iain