mysql - 'a1.location' 中的未知列 'where clause'

Question

我正在尝试执行此查询

UPDATE airport AS a1, 
(SELECT location_ar 
FROM airport as a3 
WHERE a3.location = a1.location AND a3.location_ar != NULL LIMIT 1) as a2 
SET a1.location_ar = a2.location_ar WHERE a1.location = NULL;

但是我收到“'where 子句'中的未知列'a1.location'”，

编辑:新查询是:

UPDATE airport AS a1, (SELECT location_ar FROM airport WHERE location = a1.location AND a3.location_ar != NULL LIMIT 1) as a2 SET a1.location_ar = a2.location_ar WHERE a1.location = NULL;

请帮忙

Answer 1

更好的方法是使用 join

update airport a1
join airport a2 on a1.location = a2.location and a2.location_ar is not NULL
set a1.location_ar = a2.location_ar
where a1.location is NULL;