Re: To create a Column ina Table with function

Hi Laurenz,

Albe Laurenz <laurenz.albe@wien.gv.at> writes:

> csanyipal@gmail.com wrote:
>> I have a table with columns: number, date-range.
>> I wish to get in this table more columns: week-day-begin, week-day-end.
>>
>> In the week-day-begin column I wish to get automatically the weekday
>> name of the first date in the date range.
>>
>> In the week-day-end column I wish to get automatically the weekday
>> name of the last date in the date range.
>>
>> How can I get these two columns by executing a function?
>> Should this function be a Dynamic Command, or a trigger?
>
> If you really need those columns materialized, it would be a trigger
> BEFORE INSERT OR UPDATE FOR EACH ROW.
>
> But why not use a view? It is normally a bad idea to keep
> redundant information around.
>
> CREATE TABLE test (i integer PRIMARY KEY, dr daterange NOT NULL);
>
> CREATE VIEW testview AS
>    SELECT i, dr,
>           EXTRACT(DOW FROM lower(dr)) AS wd_start,
>           EXTRACT(DOW FROM upper(dr)) AS wd_end
>    FROM test;
>
> INSERT INTO test VALUES (1, '[1968-10-20,2050-04-01]');
>
> SELECT * FROM testview;
>
>  i |           dr            | wd_start | wd_end
> ---+-------------------------+----------+--------
>  1 | [1968-10-20,2050-04-02) |        0 |      6
> (1 row)

Thanks, but this gives no names of weekdays but just numbers.

How can I get the name ( eg. Monday ) of the weekday in this view?

Regards, from Pal