Re: add constraints to views

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Please consider the following situation.

CREATE TABLE test_table (
~ id SERIAL PRIMARY_KEY,
~ tag BOOLEAN,
~ field1 INTEGER
);

CREATE VIEW test_view (
~ SELECT * FROM test_table WHERE tag
);

Now I want ad a NOT NULL constraint to the view on field1. I tryed the
following, but neither works.

ALTER TABLE test_view ADD CONSTRAINT isit CHECK ( field1 IS NOT NULL);
ALTER TABLE test_view ALTER field1 SET NOT NULL;

How can I do this?

Regards

Andreas
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Andreas Fromm wrote:

> CREATE VIEW test_view (
> ~ SELECT * FROM test_table WHERE tag
> );
>
> Now I want ad a NOT NULL constraint to the view on field1. I tryed the
> following, but neither works.

what does mean add a null constrain to a view ? Do you mean
filter out the records with the field1 null ?

CREATE OR REPLACE test_view AS
SELECT *
FROM test_table
WHERE field1 IS NOT NULL AND
tag;

Regards
Gaetano Mendola

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Gaetano Mendola wrote:
| Andreas Fromm wrote:
|
|> CREATE VIEW test_view (
|> ~ SELECT * FROM test_table WHERE tag
|> );
|>
|> Now I want ad a NOT NULL constraint to the view on field1. I tryed the
|> following, but neither works.
|
|
| what does mean add a null constrain to a view ? Do you mean
| filter out the records with the field1 null ?
|
| CREATE OR REPLACE test_view AS
| SELECT *
| FROM test_table
| WHERE field1 IS NOT NULL AND
| tag;
|
No, I mean that the view behaves like a table with the same columns as
table, but that restricts to records on wich tag is set. To insert a
record to this "special" table it requires to have field1 set. In other
words: A record of table is a record of view if tag is set. If tag is
set, then field1 has also have to have a value. If tag is not set, it
may have a value for field1, but will not show up in the view. Of course
I could achive this be triggers, but I thought it could be possible to
do via constraints on the view.

Regards

Andreas
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Andreas Fromm <Andreas(dot)Fromm(at)physik(dot)uni-erlangen(dot)de> writes:
> No, I mean that the view behaves like a table with the same columns as
> table, but that restricts to records on wich tag is set. To insert a
> record to this "special" table it requires to have field1 set. In other
> words: A record of table is a record of view if tag is set. If tag is
> set, then field1 has also have to have a value. If tag is not set, it
> may have a value for field1, but will not show up in the view. Of course
> I could achive this be triggers, but I thought it could be possible to
> do via constraints on the view.

Constraints on a view are meaningless --- it has no real rows to
constrain. Put the constraints on the underlying table.

regards, tom lane