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Databases :: MySql :: Insert and/or update.
By: RQuadling U.S.A.  Date: 06/03/2003 00:00:00  English  Points: 100 Status: Answered
Quality : Excellent
Simplistically, I have some data which equates to 1 row in table.

If the row exists (I have a key which is unique for this data and is used as the primary key for the table), then I want to update some of the fields.

If the row does NOT exist, I want to add all the data.

What is the most effecient way to do this as an SQL statement?

Can it be done in 1 statement?

I am using PHP (if that helps).

Regards,
By: VGR Date: 06/03/2003 03:20:00 English  Type : Answer
ok
first in two statements, I won't offense you in telling you how to do the check (with mysql_num_rows() for instance) of existence of the line, then either UPDATE or INSERT it :D

Now in one statement only... Using IF EXISTS perhaps

I thought soem time ago that an UPDATE would in fact do an INSERT if the key did not pre-exist, but I'm not sure... I would try if I were you.
By: Squibi Date: 06/03/2003 04:32:00 English  Type : Comment
You have to use two statments. UPDATE won't do INSERT if key you choose don't exist.
There is a resolution - you can prepare set of keys (for example in one loop), buy you have to control if number of records filled with data is lesser than number of keys - in that case you have to increase number of pre-created records in your table. IMHO - it's not a good idea, so do it if you REALLY have to use one statement.
By: sumotimor Date: 06/03/2003 06:39:00 English  Type : Comment
REPLACE should fit yours needs :

<A HREF="http://www.mysql.com/doc/en/REPLACE.html">http://www.mysql.com/doc/en/REPLACE.html</a>
By: VGR Date: 06/03/2003 19:23:00 English  Type : Comment
YES ! That's what I was thinking of when stupidly fast-writing about UPDATE doing an INSERT :D
hu hu hu stupid me
By: TheFalklands Date: 06/03/2003 19:37:00 English  Type : Comment
REPLACE does not ever do an update - at most a DELETE and then an INSERT.

So REPLACE would work if you dont care about the old row...
By: sumotimor Date: 06/03/2003 19:55:00 English  Type : Comment
you're right ultraslacker for the delete and insert.
but if you want to replace a row you shouldn't care about the old row.

of course you could have problems if you have an autoincremented primary key
and there is a foreign key based upon this key (the new record have a new autoincrement value).

In all others cases (99% in my opinion) all should be fine.
By: RQuadling Date: 07/03/2003 22:00:00 English  Type : Comment
The best method I've come up with is this ...

// Does the item already exist?
$sQuery = "SELECT COUNT(Item.ID) AS ItemCount FROM Items WHERE Items.ID=$iAIID;";
$result = mysql_query($sQuery) or die('Invalid check query - ' . mysql_error());
$row = mysql_fetch_assoc($result);
mysql_free_result($result);
$sAIDescription = addslashes($sAIDescription);
if ($row['ItemCount'] == 0)
{
$sQuery = "INSERT INTO Items(ID,Description,Done) VALUES ($iAIID, '$sAIDescription',0)";
$aCount['Items']++;
}
else
{
$sQuery = "UPDATE Items SET Description='$sAIDescription' WHERE ID=$iAIID";
}
if (($row['ItemCount'] == 0) || (strlen($sAIDescription) > 0))
{
$result = mysql_query($sQuery) or die('Invalid update query - ' . mysql_error());
}

Any advances?

Regards,

Richard.
By: VGR Date: 07/03/2003 22:36:00 English  Type : Comment
that's exactly the path I would have followed. It's your (dispreffred) option "in two statement). That's what I wrote in the first answer. Checking for existence with mysql_num_rows() on a SELECT, then choosing either to INSERT INTO, either to UPDATE

Classical solution to a classical problem
By: RQuadling Date: 11/03/2003 20:51:00 English  Type : Comment
I would have preferred an atomic method.

Ho hum!

Thanks all.

Richard.
By: VGR Date: 11/03/2003 21:17:00 English  Type : Comment
I'm afraid there is none using pure SQL

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