Question

我有一张这样的表：

// names
+----+-------+
| id |  name |
+----+-------+
| 1  | jack  |
| 2  |       |
+----+-------+

这是预期的结果：

// names
+----+-------+
| id |  name |
+----+-------+
| 1  | jack  |
| 2  | jack  |
+----+-------+

这是我的疑问：

update names set name = ( select name from names where id = 1 ) where id = 2

但它抛出：

错误1093（HY000）：您无法指定目标表＆＃39;名称＆＃39;用于FROM子句中的更新

我该怎么做？

Answer 1

您必须使用别名加入同一个表：

UPDATE names as t1
INNER join (select name from names where id = 1) t2
SET t1.name = t2.name
WHERE t1.id = 2

Answer 2

你可以通过嵌套子查询来欺骗MySQL：

update names 
set name = select name from ( select name from names where id = 1 ) as t
where id = 2

或者，您可以使用CROSS JOIN：

UPDATE names n
CROSS JOIN (
  SELECT name FROM names WHERE id = 1) AS t
SET 
    n.name = t.name
WHERE id = 2