Question

我写了这个并得到了错误，只是启动了sql，所以我不知道是什么问题。数据库是sakila-https://dev.mysql.com/doc/sakila/en/sakila-structure.html，查询是要找到在电影“ AFRICAN EGG”中扮演的演员的名字

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Answer 1

您需要在where语句中包含一个比较

SELECT a.first_name, a.last_name
FROM actor a
WHERE a.actor_id in      -- probably actor id
    (SELECT actor_id
     FROM film_actor 
     WHERE film_id in    -- probably film id
        (SELECT film_id
         FROM film
         WHERE title = "AFRICAN EGG"))

您也可以通过联接来实现

SELECT a.first_name, a.last_name
FROM actor a join film_actor fa on
    a.actor_id = fa.actor_id
  JOIN film f ON
    fa.film_id = f.film_id
WHERE f.title = "AFRICAN EGG";

Answer 2

根据您的要求使用以下查询。

SELECT a.first_name, a.last_name
FROM actor a
WHERE a.id IN
    (SELECT fa.actor_id
     FROM film_actor fa
     WHERE fa.film_id IN
        (SELECT film_id
         FROM film
         WHERE title = "AFRICAN EGG"))

SELECT 
    a.first_name,
    a.last_name
FROM actor a 
JOIN film_actor fa ON fa.film_actor = a.id
JOIN film f ON f.id = fa.film_id
WHERE f.title = "AFRICAN EGG";

子查询在我的代码中返回多于1行

2 个答案: