Re: Alter table column constraint

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От Melvin Davidson
Тема Re: Alter table column constraint
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Msg-id CANu8FiwEGtZWAbwAHOuU7e09QFSCNJAHfRGOnxmRNxZtf29k2A@mail.gmail.com
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Ответ на Re: Alter table column constraint  (Rich Shepard <rshepard@appl-ecosys.com>)
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So CREATE a table eg:
CREATE TABLE fks_for_tables
( fks_id serial
  fks_values varchar(20),
 CONSTRAINT fks_pkey PRIMARY KEY (fks_id),
 CONSTRAINT fks-unique UNIQUE fks_values
)

Then
INSERT INTO fks_for_tables
(fks_values)
VALUES
( 'Agriculture'),
('Business'),
('other))',
'Chemicals')
...
...
('Transportation');

Then you can
ALTER TABLE your_table
ADD CONSTRAINT FOREIGN KEY (industry)
REFERENCES fks_for_tables(fks_valies);




On Mon, Dec 17, 2018 at 3:20 PM Rich Shepard <rshepard@appl-ecosys.com> wrote:
On Mon, 17 Dec 2018, Melvin Davidson wrote:

> Yes, you must drop then add the revised constraint. However, from your
> statement above, it sounds to me as if you would be better off using A
> FOREIGN kEY CONSTRAINT. It makes things a lot simpler.

Melvin,

   I don't follow. Here's the DDL for that column:

industry varchar(24) NOT NULL
     CONSTRAINT invalid_industry
     CHECK (industry in ('Agriculture', 'Business, other', 'Chemicals',
     'Energy', 'Law', 'Manufacturing', 'Mining', 'Municipalities',
     'Ports/Marine Services', 'Transportation')),

and I want to remove Municipalities for the more general Government.

Regards,

Rich



--
Melvin Davidson
Maj. Database & Exploration Specialist

Universe Exploration Command – UXC

Employment by invitation only!

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