使用单个查询在更新时自动增加MySQL列字段 - Auto-increment MySQL column field on update using a single query

Auto-increment MySQL column field on update using a single query

假设我有以下代码:

$ids = execute_query("SELECT id FROM table WHERE field = 'value' ORDER BY order_field");
$query = "UPDATE table SET increment = CASE";
for ($i = 0; $i <= sizeof($ids); $i++) {
  $query .= " WHEN id = " . $ids[$i] . " THEN " . $i;
}
$query .= " END WHERE field = 'value'";

然后执行该查询。

是否有一种方法将SELECT和UPDATE组合成一个查询，有效地实现完全相同的事情?

在子查询同一表时更新表是不可能的:http://dev.mysql.com/doc/refman/5.6/en/update.html "目前，您不能在子查询中更新表并从同一表中进行选择。"

我没有在这里运行，但据我所知，这是你想要的:

SET @ordering = 0;
UPDATE
  table SET increment = (@ordering := @ordering + 1)
WHERE
  field = 'value'
ORDER BY
  order_field;

您可以在单独的查询中执行SET和UPDATE，只要您不重新连接数据库。

这可能是你想要的:

update table
    set increment = (select cnt
                     from (select count(*) as cnt
                           from table t
                           where field = 'value' and t.id <= table.id
                          ) a
                    )
    where field = 'value';

SET @ordering = 100000;
UPDATE candidate 
    SET regno = (@ordering := @ordering + 1)
    WHERE 
        year = 2014 AND 
        confirm = 1 AND
        e_stat = 1 
    ORDER BY centre_code, `name`;