Question

开始表

knowledge_base

knowledge_id
sub_body_part_id
symptom
disease
specialization_id
gender
age
last_update

main_body_part

main_body_part_id
main_body_part
last_update

sub_body_part

sub_body_part_id
sub_body_part
last_update

专业化

specialization_id
specialization
last_update

sub_body_part_has_main_body_part

sub_body_part_id
main_body_part_id

结束表

这是我的查询。这似乎是正确的，但我没有得到main_body_part表，我也不知道如何查询它。对不起，我是这种情况的初学者。请给我同样的解决方案，我很感激。 :)

SELECT sbp.sub_body_part, s.specialization, k.symptom, k.disease, k.gender, k.age
from knowledge_base k
left join sub_body_part sbp on sbp.sub_body_part_id = k.sub_body_part_id
left join specialization s on s.specialization_id = k.specialization_id

这是一个例子：

          Main body   | Sub body |  Disease |  symptom  |  specialization  |   gender   |   age  


           Head          Eyes        Stroke     Confusion      Neurology        Both        All

Answer 1

现在您已将映射表从sub添加到main，请尝试：

SELECT mbp.main_body_part, sbp.sub_body_part, s.specialization, k.symptom, k.disease, k.gender, k.age
from knowledge_base k
left join sub_body_part sbp on sbp.sub_body_part_id = k.sub_body_part_id
left join sub_body_part_has_main_body_part s2m on s2m.sub_body_part_id = sbp.sub_body_part_id
left join main_body_part mbp on mbp.main_body_part_id = s2m.main_body_part_id
left join specialization s on s.specialization_id = k.specialization_id

如何在mysql中查询多个表？

1 个答案: