H2 MERGE: Column not found

Question

I've got the following table:

create table companies (id identity, version int not null, last_modified timestamp not null);
insert into companies (version, last_modified) values (0, NOW());

I then create a PreparedStatement and supply a value for index 1:

merge into companies (id, version, last_modified) values(?, version + 1, NOW())

H2 fails with this error:

Column "VERSION" not found

I understand that H2 doesn't like version + 1 on the right-hand side, but it's not clear how to return 0 for new rows and version + 1 for existing rows. Is there an easier way than using a select statement with a union?

Answer 1

You could use:

merge into companies (id, version, last_modified) 
values(?, coalesce((select version + 1 from companies where id = ?), 0), NOW())

Answer 2

Thomas's answer of

merge into companies (id, version, last_modified) 
values(?, coalesce((select version + 1 from companies where id = ?), 0), NOW())

Becomes rather cumbersome if you (as I do) want to conditionally insert or update several fields - you need a coalesce((select ...), default) for each one!

It would appear that a more general answer needs to be two statements:

MERGE INTO companies (id) key (id) VALUES (?)
UPDATE companies SET version=1+IFNULL(version,0), otherfields... WHERE id=?

In other words: don't use MERGE for multiple conditional changes (where you need an expression and not just a value) in a record.

I'd love to be proven wrong on this...