Question

我有两张桌子：

TABLE：城市

city_id,  lat,  lon, name,  country_id

TABLE：国家

country_id,  name

我想要一个返回的SQL查询：

cities.lat,  cities.lon,   cities.name,  countries.name(for the corresponding cities.country_id)

我发誓这一定很容易。但我无法让它发挥作用。

Answer 1

您可以使用连接。也总是使用表名的别名来理解简单和标准的规则。

select 
    ci.lat,  ci.lon, ci.name,  cn.name
from 
    city ci
inner join 
    countries cn on ci.country_id = cn.country_id

Answer 2

如果我明白了，那就是查询。

SELECT cities.lat, cities.lon, cities.name, countries.name
FROM cities INNER JOIN countries
ON cities.country_id = countries.country_id

顺便说一下，从cities.country_id引用countries.country_id的名称可以看出，您应该明确说明。

Answer 3

这就是我使用子查询解决它的方法。但是使用上面的Ajay2707和marc_s给出的答案。它产生相同的结果。我把我的答案仅供参考（子查询）：）

SELECT cities.name AS city, cities.lon, cities.lat, (SELECT countries.name AS country FROM countries WHERE countries.country_id=cities.country_id ) AS country FROM cities

Answer 4

SELECT 
   ct.name, ct.lat, ct.lon, cnt.name 
FROM
   cities ct, countries cnt 
WHERE 
   ct.country_id = cnt.country_id


[Using Join Keyword]

SELECT ct.name, ct.lat, ct.lon, cnt.name 
FROM cities ct
INNER JOIN countries cnt
ON ct.country_id = cnt.country_id;

Answer 5

select 
   a.name, a.country_id, b.cities, b.city_id, b.lat, b.lon, b.name 
from 
   cities b, countries a 
where 
   b.country_id = a.country_id

两个表中的SQL查询

5 个答案: