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Date: Mon, 22 Apr 2024 09:16:26 -0700
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Subject: Re: adding a generated column to a table?
To: Celia McInnis <celia.mcinnis@gmail.com>,
 "pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <CAGD6t7L3W=ftbvkrWRHwAAT0SAwdC0AWiw7oek7hRWMrBU9dUQ@mail.gmail.com>
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On 4/22/24 09:05, Celia McInnis wrote:
> If I have a table containing a date field, say:
> create temporary table tmp1 as select now()::date as evtdate;
> SELECT 1
> 
> select DATE_PART('year', evtdate)::integer as year from tmp1;
>   year
> ------
>   2024
> (1 row)
> 
> Is there some way of doing something like the following?:
> 
> alter table tmp1 add column year integer generated always as 
> DATE_PART('year', evtdate)::integer STORED;
> ERROR:  syntax error at or near "DATE_PART"
> LINE 1: ... tmp1 add column year integer generated always as DATE_PART(...
> 

https://www.postgresql.org/docs/current/sql-createtable.html

GENERATED ALWAYS AS ( generation_expr ) STORED

So:


generated always as (DATE_PART('year', evtdate)::integer) STORED

-- 
Adrian Klaver
adrian.klaver@aklaver.com