On Tue, 24 Sep 2013 20:21:09 +0200
Petite Abeille <petite.abei...@gmail.com> wrote:
> On Sep 24, 2013, at 8:05 PM, Simon Slavin <slav...@bigfraud.org>
> wrote:
>
> > Which is why you do an INSERT first, and allow it to fail, then do
> > the UPDATE.
>
> Sure. A lot of error proce procedural code to do what one SQL
> statement could do much more naturally.
Which is why you should
update T where exists (select 1 from source ...)
insert into T ... select ... where not exists [in T]
Because this question comes up quite often, I added a discussion
about it to my canonical sql page at
http://www.schemamania.org/sql/#some.rows.
No procedural code, no forced errors, and no dodgy semantics. Test rows
affected if you want to skip the insert in the cases where all rows are
updated.
--jkl
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