Question

我遇到以下问题：我尝试选择用户所做的所有投票并将其放在一列中。我为此使用GROUP_CONCAT，但不知何故它混合了值的顺序。

这是SQL代码：

SELECT 
    GROUP_CONCAT(DISTINCT options.option_name SEPARATOR ',') AS selected,
    user_login.firstname, user_login.lastname,
    event.event_title
FROM
    options, user_login, event, votes, questions
WHERE
    event.id = ? AND questions.Event_id = event.id 
    AND votes.user_id = user_login.id AND votes.question_id = questions.id 
    AND FIND_IN_SET(options.id, selected)

GROUP BY user_login.id 订购 user_login.class

投票的示例值是：

id |  event_id  | question_id  |  selected   |  user_id
25       14           42          52,46,41         1
26       14           43             68            1

选项如：

id |  option_name   | question_id
 40        Project A          42
 41        Project B          42
 46        Project C          42     
 52        Project D          42
 67        Hello              43
 68        Bye                43

问题就像：

id  |  question_name  | event_id
42     Project Number       14
43     Greeting             14

事件就像：

id  |  title
14     Project Testing

给定代码的输出是：

selected                            |  event_title
Project C, Bye, ProjectD, Project B      Test

如何保留原始订单，以便输出我：项目D，项目C，项目B，再见？

Answer 1

会是这样的吗？基本上你说字段值的顺序，使它们看起来像'52'，'46'，......等等。

SELECT 
    GROUP_CONCAT(DISTINCT options.option_name 
                 ORDER BY FIELD( options.id, 
                                 concat('"', 
                                        replace(selected, ',', '","'),
                                        '"') 
                               ) 
                 SEPARATOR ','
                ) AS selected,
    user_login.firstname, user_login.lastname,
    event.event_title
FROM options, user_login, event, votes, questions
WHERE event.id = ? AND questions.Event_id = event.id 
  AND votes.user_id = user_login.id AND votes.question_id = questions.id 
  AND FIND_IN_SET(options.id, selected)
GROUP BY user_login.id
ORDER BY user_login.class

修改

我这样做的首选方法是创建一个包含字符串的变量..它更容易阅读，你可以确保它以这种方式执行正确的顺序..

SET @order_field := ( SELECT group_concat( CONCAT('"', replace(selected, ',', '","'), '"') ) FROM votes);

然后查询会更容易阅读...

SELECT GROUP_CONCAT(DISTINCT options.option_name ORDER BY FIELD( options.id, @order_field) SEPARATOR ',' ) AS selected, user_login.firstname, user_login.lastname, event.event_title FROM options, user_login, event, votes, questions WHERE event.id = ? AND questions.Event_id = event.id AND votes.user_id = user_login.id AND votes.question_id = questions.id AND FIND_IN_SET(options.id, selected) GROUP BY user_login.id ORDER BY user_login.class

MYSQL - GROUP_CONCAT和FIND_IN_SET是混合值/顺序？

1 个答案: