MySQL的：更新具有與最大值

Question

我想更新最後生成的行（max(id)排「其中」子句的表

我想這個代碼，但它不工作

update person t1 
set t1.age = 25 
where t1.id = (select max(t2.id) from person t2 
      where t2.address = 'LA, California'); 

。

MySQL的告訴我說：Error Code: 1093. You can't specify target table 't1' for update in FROM clause

所以，我想，我不能在執行操作如更新達到同樣的故事

如何℃。我唯一的這個問題？

問候。

Answer 1

你可以爲嘗試：

UPDATE person t1 
    INNER JOIN (SELECT MAX(id) AS id FROM person 
      WHERE t2.address = 'LA, California') t2 
     ON t1.id = t2.id 
SET t1.age = 25; 

或

SELECT MAX(t2.id) 
INTO @var_max_id 
FROM person t2 
WHERE t2.address = 'LA, California'; 

UPDATE person t1 
SET t1.age = 25 
WHERE t1.id = IFNULL(@var_max_id, -1); 

Answer 2

不能引用同一個表中的子查詢，但可以改爲做一個JOIN（在UPDATE和DELETE聲明允許）：

UPDATE person a 
JOIN (SELECT MAX(id) AS id FROM person WHERE address = 'LA, California') b 
     ON a.id = b.id 
SET a.age = 25 

另一種方式，你可以做到這一點是通過使用在ORDER BY/LIMIT技術：

UPDATE person 
SET  age = 25 
WHERE address = 'LA, California' 
ORDER BY id DESC 
LIMIT 1