如何将多个MySQL行连接到一个字段中？

使用

MySQL

，我可以执行以下操作：

SELECT c.id_category, c.id_category_type, c.label, c.id_parent
FROM category c
WHERE  c.id_category_type < 3 
ORDER BY c.id_category_type;

但是相反，我只想要

concat

行，我有一个

id\u类别

和

id\u父项

示例：

我在上查找了一个函数，它看起来不像

CONCAT

或

CONCAT\WS

函数接受结果集，那么这里有人知道如何执行此操作吗？

测试此操作：

SELECT category.id_category, category.id_category_type, 
CONCAT(category.label, '-', parents.label), category.id_parent  FROM category INNER JOIN
(SELECT id_category AS id, label FROM category WHERE id_parent = -1) AS parents
ON parents.id = category.id_parent WHERE  category.id_category_type < 3 
ORDER BY category.id_category_type;

然后，您可以像使用任何其他表一样使用“父”表并构建联接查询

Autre-Demande d'information
Mairie-Demande d'information
Stationnement-Demande d'information
Autre-Réclamation
Familles-Réclamation
TESTDOMAINE-TEST

SELECT category.id_category, category.id_category_type, 
CONCAT(category.label, '-', parents.label), category.id_parent  FROM category INNER JOIN
(SELECT id_category AS id, label FROM category WHERE id_parent = -1) AS parents
ON parents.id = category.id_parent WHERE  category.id_category_type < 3 
ORDER BY category.id_category_type;

(SELECT id_category AS id, label FROM category WHERE id_parent = -1) AS parent