Comments on: Update Multiple Rows With Different Values and a Single SQL Query

By: CAP Marketer - 10 astuces SQL pour accélérer vos bases de données

CAP Marketer - 10 astuces SQL pour accélérer vos bases de données — Fri, 03 Sep 2010 22:16:42 +0000

[...] Source: http://www.karlrixon.co.uk/articles/sql/update-multiple-rows-with-different-values-and-a-single-sql-... [...]

By: Karl

Karl — Thu, 02 Sep 2010 17:31:44 +0000

@Jay

The limit in the number of case statements does not mean the number of rows which can be updated is limited to 255 – the two factors are not necessarily related. You might have 10 case statements which could match 100000 rows each for example. If you are trying to target a single row per case statement then you may have an issue however. If this is the case you would probably be better off moving the conditions into their own table and joining to achieve the same thing:

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category_order_helper
category_id | display_order
-------------+----------------
1 | 6
2 | 4

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UPDATE categories
SET display_order = h.display_order
INNER JOIN category_order_helper AS h
ON categories.id = h.category_id

It requires a couple of extra queries (a TRUNCATE and an INSERT), but it avoids the case statement limit.

By: Jay

Jay — Thu, 02 Sep 2010 16:01:48 +0000

The use of the CASE statement to update multiple records only works, if you’re updating less than 255 rows – there is a limit on the number of CASE statements you can use.
So, if you have more than 255 rows to update, then just write it as multiple queries, using the very first syntax described above.

By: zflag

zflag — Fri, 13 Aug 2010 18:39:56 +0000

Kirk: your query doesn’t work because your CASE statement is evaluating the same field you are trying to update.

By: Kirk

Kirk — Thu, 29 Jul 2010 23:47:42 +0000

Not Working.
Using MS Access

UPDATE navItems
SET navItems.pos = CASE navItems.pos WHEN 10 THEN 2 WHEN 25 THEN 10 WHEN 24 THEN 13 ELSE 0 END
WHERE (pos IN (10, 25, 24))

Receiving a syntax error.

Any ideas?

Kirk

By: bruno negrao

bruno negrao — Tue, 29 Jun 2010 17:44:29 +0000

great post, thank you.

By: Colin

Colin — Mon, 28 Jun 2010 15:25:38 +0000

Anyone know how to program this exact same thing using C# for ASP.NET and maybe ACCESS DB for now?

By: Tacaza

Tacaza — Sat, 26 Jun 2010 16:44:05 +0000

I’m also doing the jQuery sortable.

I was going to implement the method described here:
http://le-gall.net/pierrick/blog/index.php/2007/11/29/108-mysql-bulk-update-with-talend-open-studio

but fortunately I came across this article. The solution described here is much simpler to implement and as I’ve tested myself, the query is very efficient, at least for me. Thank you very much for the post.

By: Feroz

Feroz — Sun, 20 Jun 2010 18:51:56 +0000

Excellent post!!!

Perfect Solution for SQL Query…

Great post

By: dralezero

dralezero — Sun, 16 May 2010 04:12:39 +0000

Thanks. I am doing the jQuery sortable so my IDs of the records I want to update are the values in my array. The array index is the ordering (keys). So I swapped the values in WHEN THEN

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$sql = "UPDATE `listitems` SET `position` = CASE `id`";
foreach ($_GET['listItem'] as $position => $id) {
$sql .= " WHEN ".$id." THEN ".$position;
$ids[] = $id;
}
$ids = implode(",",$ids);
$sql .= " END WHERE `id` IN ($ids)";