sql - 在 SQL 中使用子查询返回每个派生表必须有自己的别名错误？

Question

我发现很难理解为什么以下查询不起作用:

SELECT rating_count 
FROM 
    (SELECT 
         title, 
         COUNT(rating) AS rating_count
     FROM series
     LEFT JOIN reviews ON series.id = reviews.series_id
     GROUP BY series.id);

子查询的结果如下:

为什么当我尝试查询 rating_count 时，它不起作用？我想我可以要求这个。我的目的是过滤那些具有 Rating_count = 0 的行。

我想尝试:

SELECT * 
FROM 
    (SELECT
         title, COUNT(rating) AS rating_count
     FROM series
     LEFT JOIN reviews ON series.id = reviews.series_id
     GROUP BY series.id) 
WHERE rating_count = 0; 

Answer 1

正如错误所述，您需要为派生表添加别名:

SELECT * FROM (
    SELECT
    title, 
    count(rating) as rating_count
    FROM series
    LEFT JOIN reviews
        ON series.id = reviews.series_id
    GROUP BY series.id
    ) AS t
WHERE rating_count=0;