如何将子查询中的字符串连接到mysql中的一行? [英] How do I concatenate strings from a subquery into a single row in mysql?

问题描述

我有三张桌子:

table "package"
-----------------------------------------------------
package_id      int(10)        primary key, auto-increment
package_name    varchar(255)
price           decimal(10,2)

table "zones"
------------------------------------------------------
zone_id         varchar(32)    primary key (ex of data: A1, Z2, E3, etc)

table "package_zones"
------------------------------------------------------
package_id     int(10)
zone_id        varchar(32)

我要做的是返回包裹表中的所有信息以及该包裹的区域列表.我想要按字母顺序排序并以逗号分隔的区域列表.

What I'm trying to do is return all the information in package table PLUS a list of zones for that package. I want the list of zones sorted alphabetically and comma separated.

所以我正在寻找的输出是这样的......

So the output I'm looking for is something like this...

+------------+---------------+--------+----------------+
| package_id | package_name  | price  | zone_list      |
+------------+---------------+--------+----------------+
| 1          | Red Package   | 50.00  | Z1,Z2,Z3       |
| 2          | Blue Package  | 75.00  | A2,D4,Z1,Z2    |
| 3          | Green Package | 100.00 | B4,D1,D2,X1,Z1 |
+------------+---------------+--------+----------------+

我知道我可以在 PHP 中使用表示层做一些事情来获得所需的结果.问题是，我希望能够对 zone_list ASC 或 DESC 进行排序，甚至使用WHERE zone_list LIKE"等等.为了做到这一点，我需要在 MYSQL 中完成.

I know I could do something in PHP with the presentation layer to get the desired result. The problem is, I would like to be able to sort zone_list ASC or DESC or even use" WHERE zone_list LIKE" and so on. In order to do that, I need this done in MYSQL.

我什至不知道如何开始解决这个问题.我尝试使用子查询，但它一直抱怨多行.我试图将多行连接成一个字符串，但显然 MySQL 不喜欢这样.

I have NO idea how to even begin to tackle this. I tried using a subquery, but it kept complaining about multiple rows. I tried to concat the multiple rows into a single string, but evidently MySQL doesn't like this.

提前致谢.

更新！

这里是给感兴趣的人的解决方案.

Here is the solution for those who are interested.

SELECT 
    `package`.*,
    GROUP_CONCAT(`zones`.`zone` ORDER BY `zones`.`zone` ASC SEPARATOR ','  )  as `zone_list`
FROM 
    `package`,
    `package_zones`
LEFT JOIN 
    (`zones`,`ao_package_zones`) ON (`zones`.`zone_id` = `package_zones`.`zone_id` AND `package_zones`.`package_id` = `package`.`package_id`)
GROUP BY 
    `ao_package`.`package_id`

推荐答案

通过使用GROUP_CONCAT() 函数和 GROUP BY 调用.这是一个示例查询

by using the GROUP_CONCAT() function and a GROUP BY call. here's an example query

SELECT 
   p.package_id,
   p.package_name,
   p.price,
   GROUP_CONCAT(pz.zone_id SEPARATOR ',') as zone_list 
FROM 
   package p 
LEFT JOIN package_zone pz ON p.package_id = pz.package_id 
GROUP BY 
   p.package_id

您应该仍然可以按 zone_id (或 zone_list)进行排序，并且可以使用 WHERE zp.zone_id = 'Z1' 来代替 LIKE 或类似的东西.

you should still be able to order by zone_id s (or zone_list), and instead of using LIKE, you can use WHERE zp.zone_id = 'Z1' or something similar.

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