On 15/09/2013 3:36 AM, Petite Abeille wrote:
On Sep 15, 2013, at 12:53 AM, Kees Nuyt <k.n...@zonnet.nl> wrote:
3) If an SQL-statement generally contains more than one reference
to one or more <datetime value function>s, then all such ref-
erences are effectively evaluated simultaneously.
FWIW, Oracle concurs:
"All of the datetime functions that return current system datetime information, such
as SYSDATE, SYSTIMESTAMP, CURRENT_TIMESTAMP, and so forth, are evaluated once for each
SQL statement, regardless how many times they are referenced in that statement."
I'm pretty sure that anything weaker breaks [the illusion of]
serializability, by giving users a way to see that their transactions
did not execute in the order they appeared to:
A: select CURRENT_TIMESTAMP; update foo set v=1 where k=0; select * from
foo;
B: update foo set v=2 where k=0; select * from foo; select
CURRENT_TIMESTAMP;
Whether that matters in practice, I wouldn't know...
Ryan
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