找出全國明智所有國家和使用連接

Question

從數據庫狀態明智的城市找出全國明智所有國家和使用連接

我在數據庫，即國家的三個表從數據庫狀態智慧城市，州，市 我使用主鍵和外鍵給它們之間的映射。 我想要特定的「印度」國家和相關國家的所有州和城市......我該怎麼辦？ 在這裏，我給我的代碼...這我created..Give我任何其他建議

select countries.name as country, 
states.name as state, 
cities.name as city 
from states inner join cities 
on states.id = cities.state_id 
inner join countries 
WHERE countries.name='India'; 

Answer 1

請使用以下查詢
表具有低於數據 -

+------+-------+ 
| id | name | 
+------+-------+ 
| 1 | india | 
| 2 | pak | 
| 3 | afgan | 
+------+-------+ 

狀態表

+------+---------+------------+ 
| id | name | country_id | 
+------+---------+------------+ 
| 1 | haryana |   1 | 
| 2 | gujrat |   1 | 
| 3 | himchal |   2 | 
+------+---------+------------+ 

城市表

+------+-------------+----------+ 
| id | name  | state_id | 
+------+-------------+----------+ 
| 1 | bahadurgarh |  1 | 
| 2 | hisar  |  1 | 
| 3 | surat  |  2 | 
| 4 | shimla  |  3 | 
+------+-------------+----------+ 




select cities.id , cities.name ,states.id , states.name ,countries.name from cities left join states on cities.state_id = states.id left join countries on states.country_id = countries.id where countries.name='india' ; 

+------+-------------+------+---------+-------+ 
| id | name  | id | name | name | 
+------+-------------+------+---------+-------+ 
| 1 | bahadurgarh | 1 | haryana | india | 
| 2 | hisar  | 1 | haryana | india | 
| 3 | surat  | 2 | gujrat | india | 
+------+-------------+------+---------+-------+ 

Answer 2

從sql查出國家明智的州和明智的城市是不是一個好主意。

，你應該用JavaScript去嘗試這種just include this file in your required webpage

Answer 3

嘗試以下（對不起，在代碼中沒有換行。不知道它是如何工作）。

Select countries.name as country, states.name as sta from countries left join cities on states.id= cities.state_id where states.country_id in (SELECT countries.id FROM countries where countries.name='India')