我知道你可以一次插入多行，是否有一种方法可以一次更新多行(如在，在一个查询)在MySQL?
编辑: 例如，我有以下内容
Name id Col1 Col2
Row1 1 6 1
Row2 2 2 3
Row3 3 9 5
Row4 4 16 8
我想将以下所有更新组合成一个查询
UPDATE table SET Col1 = 1 WHERE id = 1;
UPDATE table SET Col1 = 2 WHERE id = 2;
UPDATE table SET Col2 = 3 WHERE id = 3;
UPDATE table SET Col1 = 10 WHERE id = 4;
UPDATE table SET Col2 = 12 WHERE id = 4;
当前回答
还没有人提到对我来说更简单的方法——使用SQL编辑器，允许你执行多个单独的查询。这张截图来自Sequel Ace，我认为Sequel Pro和其他编辑器可能有类似的功能。(当然，这是假设你只需要一次性运行它，而不是作为应用程序/网站的集成部分)。
其他回答
使用临时表
// Reorder items
function update_items_tempdb(&$items)
{
shuffle($items);
$table_name = uniqid('tmp_test_');
$sql = "CREATE TEMPORARY TABLE `$table_name` ("
." `id` int(10) unsigned NOT NULL AUTO_INCREMENT"
.", `position` int(10) unsigned NOT NULL"
.", PRIMARY KEY (`id`)"
.") ENGINE = MEMORY";
query($sql);
$i = 0;
$sql = '';
foreach ($items as &$item)
{
$item->position = $i++;
$sql .= ($sql ? ', ' : '')."({$item->id}, {$item->position})";
}
if ($sql)
{
query("INSERT INTO `$table_name` (id, position) VALUES $sql");
$sql = "UPDATE `test`, `$table_name` SET `test`.position = `$table_name`.position"
." WHERE `$table_name`.id = `test`.id";
query($sql);
}
query("DROP TABLE `$table_name`");
}
你可以给同一个表添加别名来给你想要插入的id(如果你正在逐行更新:
UPDATE table1 tab1, table1 tab2 -- alias references the same table
SET
col1 = 1
,col2 = 2
. . .
WHERE
tab1.id = tab2.id;
此外，显然还可以从其他表进行更新。在本例中，更新将兼任“SELECT”语句，从指定的表中提供数据。您在查询中显式地声明了更新值，因此第二个表不受影响。
这个问题很老了，但我想用另一个答案来扩展这个话题。
我的观点是，实现它的最简单的方法是用一个事务包装多个查询。这句话的意思是:ON DUPLICATE KEY UPDATE是一个很好的黑客，但人们应该意识到它的缺点和限制:
As being said, if you happen to launch the query with rows whose primary keys don't exist in the table, the query inserts new "half-baked" records. Probably it's not what you want If you have a table with a not null field without default value and don't want to touch this field in the query, you'll get "Field 'fieldname' doesn't have a default value" MySQL warning even if you don't insert a single row at all. It will get you into trouble, if you decide to be strict and turn mysql warnings into runtime exceptions in your app.
I made some performance tests for three of suggested variants, including the INSERT ... ON DUPLICATE KEY UPDATE variant, a variant with "case / when / then" clause and a naive approach with transaction. You may get the python code and results here. The overall conclusion is that the variant with case statement turns out to be twice as fast as two other variants, but it's quite hard to write correct and injection-safe code for it, so I personally stick to the simplest approach: using transactions.
编辑:Dakusan的发现证明我的性能估计不太有效。请参阅另一个更详细的研究的答案。
您可能还对在更新上使用连接感兴趣，这也是可能的。
Update someTable Set someValue = 4 From someTable s Inner Join anotherTable a on s.id = a.id Where a.id = 4
-- Only updates someValue in someTable who has a foreign key on anotherTable with a value of 4.
编辑:如果要更新的值不是来自数据库中的其他地方，则需要发出多个更新查询。
是的，这是可能的-你可以使用INSERT…重复密钥更新。
举个例子:
INSERT INTO table (id,Col1,Col2) VALUES (1,1,1),(2,2,3),(3,9,3),(4,10,12)
ON DUPLICATE KEY UPDATE Col1=VALUES(Col1),Col2=VALUES(Col2);
