Question

现在，我正在尝试从表中的列中获取最高值然后递增它（+1），然后将同一列的另一个记录更新为该数字。我用PHP编写脚本，将变量$ SQL发送给MySQL。

    $SQL="
        UPDATE `router`
        SET `Line Order`= (SELECT 1 + IFNULL(MAX(`Line Order`), 0) FROM `router`)
        WHERE `RN`=?
    ";
    $stmt = $GLOBALS['mySQLConnection']->prepare($SQL);
    echo $GLOBALS['mySQLConnection']->error;

错误是：您无法在FROM子句中为更新指定目标表'router' 如果不在php中编写单独的查询，我们怎么想这样做呢？

Answer 1

尝试此查询：

UPDATE router AS r1
INNER JOIN (
    SELECT 1 + IFNULL(MAX(`Line Order`), 0) AS new FROM `router`) AS r2
SET `Line Order` = r2.new
WHERE `RN` = ?

带有选择数据的MySQL更新表

1 个答案: