1.场景：主表一条数据，字表多条数据。需要查询时候展示一条，字表的数据用逗号分隔
sql语句：
SELECT
cdu.user_name as user_name,
cmp.user_id as create_uid,
cmr.receive_user_id as receive_user_id,
cmp.id as id, cmp.mesage_title as mesage_title,
cmr.status as status, cmp.create_time as create_time,
cmp.message_content as message_content,
cmp.status as message_status,
IFNULL(GROUP_CONCAT(DISTINCT cmd.doc_name),‘‘) as docName
FROM car_message_post cmp
LEFT JOIN car_message_receiver cmr ON cmp.id = cmr.message_id
INNER JOIN car_adm_user cdu ON cmp.user_id = cdu.user_id
LEFT JOIN car_message_doc cmd ON cmd.message_id = cmp.id
WHERE
1=1 and cmp.id = 252
GROUP BY cmp.id,mesage_title,cmp.create_time,message_content LIMIT 50;
GROUP_CONCAT(DISTINCT cmd.doc_name) 需要加上distinct,要不然字表出现重复数据
原文：https://www.cnblogs.com/thinkingandworkinghard/p/12402322.html
如果您也喜欢它,动动您的小指点个赞吧
602392714
清零编程群