Mysql 使用ORDER BY对_CONCAT进行分组，但结果不按顺序排列

上面的查询工作正常，但是

图像

列没有按优先级排序，无法理解为什么会发生这种情况

SELECT
*,
(SELECT
GROUP_CONCAT(url SEPARATOR '$$' )
FROM project_photos
WHERE project_id = projects.id
ORDER BY priority) AS images
FROM projects
WHERE catID = 2
LIMIT 0,5

---

在应用聚合函数（如

GROUP\u CONCAT（）

）后，使用

ORDER BY

进行排序。要对

GROUP_CONCAT（）

的结果进行排序，请将其放入参数中：

// Structure for table project is
CREATE TABLE `projects` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`catID` int(11) NOT NULL,
`title` varchar(255) NOT NULL,
`description` varchar(400) NOT NULL,
`url` varchar(255) DEFAULT NULL,
`tags` varchar(255) DEFAULT NULL,
`featured` varchar(3) NOT NULL DEFAULT 'No',
`featured_url` varchar(255) DEFAULT NULL,
`order` int(11) DEFAULT NULL,
`created_at` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
KEY `catID` (`catID`),
CONSTRAINT `FK_catID` FOREIGN KEY (`catID`) REFERENCES `category` (`catID`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=48 DEFAULT CHARSET=latin1;


// Structure for table project_photos is

CREATE TABLE `project_photos` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`url` varchar(250) DEFAULT NULL,
`project_id` int(11) DEFAULT NULL,
`priority` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=347 DEFAULT CHARSET=utf8;

---

尝试在

组内使用
ORDER BY

SELECT
GROUP_CONCAT(url ORDER BY priority SEPARATOR '$$')
FROM project_photos
WHERE project_id = projects.id

您应该将
order by
子句放在组concat中：

SELECT
*,
(SELECT
GROUP_CONCAT(url ORDER BY priority SEPARATOR '$$' )
FROM project_photos
WHERE project_id = projects.id
) AS images
FROM projects
WHERE catID = 2
LIMIT 0,5

外部的
orderby
正在对不同的行进行排序。因为你只有一个，它什么也不做。在group concat中，它将对由
group by
子句创建的组元素进行排序

GROUP_CONCAT(url SEPARATOR '$$' ORDER BY priority)