1. 确认group_contact表是否存在并且已正确引入
2. 确认group_contact表中列名是否正确，例如应将group_contact_id改为group_id
3. 如果是在SELECT语句中使用group_contact，请使用GROUP_CONCAT函数将多个行合并为一行，以避免错误的结果。

示例代码：

CREATE TABLE groups ( id INT PRIMARY KEY, name VARCHAR(50) );

CREATE TABLE contacts ( id INT PRIMARY KEY, name VARCHAR(50) );

CREATE TABLE group_contact ( group_id INT, contact_id INT, FOREIGN KEY (group_id) REFERENCES groups(id), FOREIGN KEY (contact_id) REFERENCES contacts(id) );

SELECT groups.name, GROUP_CONCAT(contacts.name SEPARATOR ',') AS contacts FROM groups JOIN group_contact ON groups.id = group_contact.group_id JOIN contacts ON group_contact.contact_id = contacts.id GROUP BY groups.id;