是否可以 select 并更新未知值？

Question

我有下表

桌子

ID      Person     Supervisor
1       Michele    2
2       James      4
3       Jacob      4
4       Francis    1

假设 Michele (1) 离开，我希望她的主管 (2) 接管 Michele 正在监督的任何人（Francis，4 岁）

SELECT id FROM TABLE WHERE supervisor = '1';

会还给我 2(Michele)

要更新我只会做

UPDATE TABLE
SET Supervisor = '2' <-- can this not be hard-coded but "selected" in an UPDATE statement?
WHERE Supervisor = '1';

Answer 1

使用自联接。

UPDATE TABLE AS t1
JOIN TABLE AS t2 ON t1.supervisor = t2.id
SET t1.supervisor = t2.supervisor
WHERE t2.id = 1

演示

Answer 2

您可以在子查询上使用内部联接

UPDATE TABLE t1 
INNER JOIN  (
   SELECT Supervisor FROM TABLE WHERE ID = '1' 
) T2 ON t2.Supervisor =  = t1.Supervisor

SET t1.Supervisor = t2.supervisor