Dan Jakubiec wrote:
Hi. I want to insert/update multiple rows into a table which has a
timestamp field, and I want to set the timestamp field in each row to the
current timestamp. However, it is important to me that all the rows I
update actually end up with the same timestamp value.
My concern is: what happens if the SQL query take a long time and the
current timestamp crosses a second boundary? For example, suppose I
issue
the following request on a very large table:
UPDATE ts SET my_timestamp=NULL;
Say that this query takes 3 seconds to complete. My questions:
1) Will all the rows have the same timestamp value? Or will some rows
have
"now", "now+1", and "now+2"?
2) Will the behavior be different if I use "my_timestamp=NOW()"?
3) If the timestamps will be different, what's the best way to make
them all
the same?
In the manual it says that all calls to now() in a query always return
the same time regardless of how many there are and how long it takes the
query to run so I am thinking that all records with an auto update time
stamp column that get changed in a single query would all have the same
time stamp. It should be easy enough to test if you have a large set of
data where an update would take a long time. I'm pretty sure it will do
what you need though and set them all the same.
--
Chris W
KE5GIX
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