Tenderness_Warm的博客

select c.customid,c.headurl,c.nickname,c.working_years,c.remarks,c.certificate, t.countTask,w.countWorks FROM custom_info c left join (select count(custom_id) as countTask,custom_id from task_info where project_status = 3 GROUP BY custom_id) t on c.custom

关键字段 GROUP_CONCAT FIND_IN_SET（字段名，参数 如 1,2,3,4） group by select s.id, s.name, s.sex, s.age, s.education, GROUP_CONCAT(j.label) AS occupation, ss.create_time as receivedTi...

select c.customid,c.headurl,c.nickname,c.working_years,c.remarks,c.certificate,t.countTask,w.countWorks FROM qqqq c left join (select count(custom_id) as countTask,custom_id from aaa where project_status = 3 GROUP BY custom_id) t on c.customid = t.custom_

1、 on条件是在生成临时表时使用的条件，它不管on中的条件是否为真，都会返回左边表中的记录。 2、where条件是在临时表生成好后，再对临时表进行过滤的条件。这时已经没有left join的含义（必须返回左边表的记录）了，条件不为真的就全部过滤掉。 ...