http://dev.mysql.com/doc/mysql/en/INSERT.html
INSERT [LOW_PRIORITY | DELAYED] [IGNORE]
[INTO] tbl_name [(col_name,...)]
VALUES ({expr | DEFAULT},...),(...),...
[ ON DUPLICATE KEY UPDATE col_name=expr, ... ]
If you specify the ON DUPLICATE KEY UPDATE clause (new in MySQL
4.1.0), and a row is inserted that would cause a duplicate value
in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row is
performed.Daevid Vincent wrote:
I'm developing a program where I try an "UPDATE ... LIMIT 1" and if mysql_affected_rows == 0, then I know nothing was updated and so I do an INSERT. I find this is much cleaner and the majority of the time, I'm going to do UPDATES, so I didn't want to waste a SELECT (even though I hear they're "cheap"). I'm doing these queries several times per second.
however... Of course UPDATE doesn't 'ERROR" if the record doesn't exist, it just didn't do anything (therefore that's why I use the mysql_num_rows() to check). The problem is that if I am actually doing an UPDATE to a record where nothing actually changed in the existing record, I still get mysql_affected_rows() equal to 0. *grrr*.
It would be extremely useful to somehow get a result of maybe -1 if I tried to update a record that didn't exist, versus a result of -2 if I tried to update a record that did exist, but mySQL didn't change anything.
I don't know exactly what I'm asking for other than a way to know the difference...
At the very least, it seems to me that if I update a record that exists already (even if no data changed), I should still get mysql_affected_rows()
0 (since in theory I matched something, even if mySQL behind the scenes
didn't change the data).
Out of curiosity, if I have a TIMESTAMP column, would that solve my problem, since mySQL should be forced to update that TIMESTAMP right?? [btw, I know I could try this idea, but I'm home and my code is at work right now and I just had the idea! ;-]
http://daevid.com
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