On Fri, Oct 27, 2017 at 2:13 PM, srielau <serge@rielau.com> wrote:
> While the standard may not require a unique index for the ON clause I have
> never seen a MERGE statement that did not have this property. So IMHO this
> is a reasonable restrictions.
The Oracle docs on MERGE say nothing about unique indexes or
constraints. They don't even mention them in passing. They do say
"This statement is a convenient way to combine multiple operations. It
lets you avoid multiple INSERT, UPDATE, and DELETE DML statements."
SQL Server's MERGE docs do mention unique indexes, but only in
passing, saying something about unique violations, and that unique
violations *cannot* be suppressed in MERGE, even though that's
possible with other DML statements (with something called
IGNORE_DUP_KEY).
What other systems *do* have this restriction? I've never seen one that did.
--
Peter Geoghegan
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