Re: update without SET ?

On Wed, Feb 3, 2016 at 11:49 AM, Michael Moore <michaeljmoore(at)gmail(dot)com>
wrote:

> I want to UPDATE a table but I will not know until run time which columns
> will be updated. I would like to do something like this:
> update mytest t (SELECT * FROM
> json_populate_record(null::mytest,'{"key":22,"header":44,"ident":66,"static01":"this","static02":"that"}'));
>
> In other words, I will be receiving a json document on an input parameter.
> The columns named in the json document can be a sub set of those that exist
> in the table.
>
>
If a key is defined but has a value of null what do you want to do?

​not fully tested...​

UPDATE mytest
SET col1 = COALESCE(src.col1, mytest.col1)
​FROM (SELECT * FROM json_populate_record(...)) src;​

json_populate_record outputs the full structure of mytest regardless of its
input so simply match every column and use COALESCE to choose between the
value in the json and the value already on the table.

Aside from the null json value issue that should work - if not you probably
need to describe your problem in more detail.

David J.