多表联查统计数字

SQL语句：

select A.*, B.count1, C.count2, D.count3 from task A
left join (select count(id) count1, askId from task_upload group by askId) B on A.id=B.askId
left join (select count(id) count2, askId from task_upload where state=1 group by askId) C on A.id=B.askId
left join (select count(id) count3, askId from task_upload where state=2 group by askId) D on A.id=B.askId

效果图

解析：讲查询数量的语句结果作为外联表和主表关联。

新知识：askId 查询ID个数 group by askId 通过id分组

补充内容：

LEFT JOIN class_teaching E ON E.classCode = A.classCode
WHERE
E.teacherId = 1

1可用teacherModel.get("id")替换

补充内容为查询改教师教学班级的信息