php - MySQL从另一个表插入随机值

Question

您好，我想将一些随机值从一个表插入到另一个表中，我的查询如下所示:

INSERT INTO `rounds`(`matchID`, `questionOneID`, `questionTwoID`, `questionThreeID`) VALUES (17,(SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 3))

问题是，mysql需要4个参数(matchID，questionOneID，...)并且只得到两个(17，(...))我如何告诉MySql它从SELECT中获取3个参数？ 我真的必须这样做吗:

INSERT INTO `rounds`(`matchID`, `questionOneID`, `questionTwoID`, `questionThreeID`) VALUES (17,(SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 1),(SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 1),(SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 1))

或者有更好的方法吗？

Answer 1

您的查询看起来正确。我会用 insert 来编写它。 。 。选择:

INSERT INTO `rounds`(`matchID`, `questionOneID`, `questionTwoID`, `questionThreeID`)
     SELECT 17,
            (SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 1),
            (SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 1),
            (SELECT `id` FROM `questions` ORDER BY RAND() LIMIT 1);

如果您想保证这三个问题不同，那么我可能会采用这种方法:

INSERT INTO `rounds`(`matchID`, `questionOneID`, `questionTwoID`, `questionThreeID`)
    SELECT 17,
           substring_index(group_concat(id order by rnd), ',', 1),
           substring(substring_index(group_concat(id order by rnd), ',', 2), ',', 11),
           substring_index(group_concat(id order by rnd), ',', -1),
    FROM (SELECT id, rand() as rnd FROM questions ORDER BY RAND() LIMIT 3) q

这会将三个随机问题放在一行上，没有重复项(除非 id 在 问题 中重复。