Question

CREATE or REPLACE VIEW myView AS
SELECT t2.film_id, t2.no_actors AS n_actor, COALESCE(t1.no_copies,0) AS n_inventory FROM
(SELECT film_id, count(film_id) AS no_copies FROM inventory GROUP BY film_id) AS t1 RIGHT OUTER JOIN 
(SELECT film_id, count(actor_id) 
AS no_actors FROM film_actor GROUP BY film_id) AS t2 
ON t2.film_id=t1.film_id;

以上查询给出了错误：

ERROR 1349 (HY000): View's SELECT contains a subquery in the FROM clause

我们如何在一个查询中为上述查询编写嵌套视图？请帮忙。提前谢谢。

Answer 1

您无法在创建视图中使用子查询，但您可以通过这种方式使用其他视图

CREATE or REPLACE VIEW myViewSub1 AS 
SELECT film_id, count(film_id) AS no_copies FROM inventory GROUP BY film_id
;


CREATE or REPLACE VIEW myViewSub2 AS 
SELECT film_id, count(actor_id) 
AS no_actors FROM film_actor GROUP BY film_id
;

CREATE or REPLACE VIEW myView AS
SELECT t2.film_id, t2.no_actors AS n_actor, COALESCE(t1.no_copies,0) AS n_inventory 
FROM  myViewSub1 AS t1 
RIGHT OUTER JOIN myViewSub2 AS t2 
ON t2.film_id=t1.film_id
;

mysql中的嵌套视图问题

1 个答案: