设置 MYSQL 之前 SELECT 的 WHERE 条件

Question

我有以下 MySQL 查询

SELECT `category` 
FROM `jeopardy_questions` 
WHERE `amount` = "$2,000" 
GROUP BY `category` 
HAVING COUNT(*) > 4 
ORDER BY RAND() LIMIT 1

这将给我一个随机类别，该类别中至少有 5 个问题。

现在我想获取该类别的所有行。 那么我该怎么做第二个 SELECT WHERE category等于从上一个查询返回的类别？

我尝试了以下但我相信 RAND() 导致它崩溃/超时。

SELECT *
FROM `jeopardy_questions`
WHERE `category` = (
    SELECT `category` 
    FROM `jeopardy_questions` 
    WHERE `amount` = "$2,000" 
    GROUP BY `category` 
    HAVING COUNT(*) > 4 
    ORDER BY RAND() LIMIT 1
)

Answer 1

您可以将上述查询用作子查询。 像这样：

SELECT *
FROM `jeopardy_questions`
WHERE `category` = (
    SELECT `category` 
    FROM `jeopardy_questions` 
    WHERE `amount` = "$2,000" 
    GROUP BY `category` 
    HAVING COUNT(*) > 4 
    ORDER BY RAND() LIMIT 1
)