From: | Blake McBride <blake1024(at)gmail(dot)com> |
---|---|
To: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Trouble incrementing a column |
Date: | 2019-11-23 21:28:37 |
Message-ID: | CABwHSOuxyDcnZ7xhj1uQYT09=94-x6O051x=_iK8hiOXoAgCrA@mail.gmail.com |
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Lists: | pgsql-general |
Greetings,
I am using PostgreSQL 10.10. I am having trouble incrementing a column for
reasons I can't see. It's probably some basic SQL thing. Your help is
appreciated.
create table my_table (
listid char(36) not null,
seq smallint not null,
item varchar(4096),
primary key (listid, seq)
);
insert into my_table (listid, seq) values ('abc', 1);
insert into my_table (listid, seq) values ('abc', 2);
-- the following works some of the time
update my_table set seq=seq+1;
-- the following doe not work for reasons I do not know
update my_table set seq=seq+1 where listid='abc';
What I get is a duplicate primary key. I wouldn't think I'd get that
because I'd think the whole thing is done in a transaction so that
duplicate checks wouldn't be done till the end (essentially).
Is there a clean way to do this?
Thanks!
Blake McBride
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