Question

SELECT people.first_name AS "First Name", people.last_name AS "Last Name", countries.name AS "Country1", territories.name AS "Territory1", cities.name AS "City1", countries.name AS "Country2", territories.name AS "Territory2", cities.name AS "City2"
FROM adb_people AS people
JOIN root_cities AS cities ON people.city1 = cities.id
AND people.city2 = cities.id
JOIN root_territories AS territories ON people.prov_state1 = territories.id
AND people.prov_state2 = territories.id
JOIN root_countries AS countries ON people.country1 = countries.id

我在这里要做的是将Country1（id）链接到Country1（名称）并仅显示名称。此代码示例仅在Country1，Territory1，City1与Country2，Territory2，City2相同时才有效

我会想象我的问题是我如何做我的加入。我是SQL方面的新手。我已经在互联网上阅读了JOINS（谷歌搜索并阅读了前几个教程），但在这种情况下，我读过的任何内容都没有任何帮助。

我真的很感激我在这里做错了什么。也许正朝着正确的方向努力？

Answer 1

每个国家/城市/地区需要2个单独的联接。下面是基本语法，您可能需要稍微更改它，因为我没有通过解析器：

SELECT people.first_name AS "First Name", people.last_name AS "Last Name", 
countries1.name AS "Country1", territories1.name AS "Territory1", cities1.name AS "City1", 
countries2.name AS "Country2", territories2.name AS "Territory2", cities2.name AS "City2"
FROM adb_people AS people
JOIN root_cities AS cities1 ON people.city1 = cities1.id
  AND people.city2 = cities1.id
JOIN root_territories AS territories1 ON people.prov_state1 = territories1.id
  AND people.prov_state2 = territories1.id
JOIN root_countries AS countries1 ON people.country1 = countries1.id
JOIN root_cities AS cities2 ON people.city2 = cities2.id
  AND people.city2 = cities2.id
JOIN root_territories AS territories2 ON people.prov_state2 = territories2.id
  AND people.prov_state2 = territories2.id
JOIN root_countries AS countries2 ON people.country2 = countries2.id

Answer 2

这样就可以了。

SELECT people.first_name AS "First Name", people.last_name AS "Last Name", countries.name AS "Country1", territories.name AS "Territory1", cities.name AS "City1", countries2.name AS "Country2", territories2.name AS "Territory2", cities2.name AS "City2"
FROM adb_people AS people
JOIN root_cities AS cities ON people.city1 = cities.id
JOIN root_cities AS cities2 ON people.city2 = cities.id
JOIN root_territories AS territories ON people.prov_state1 = territories.id
JOIN root_territories AS territories2 ON people.prov_state2 = territories.id
JOIN root_countries AS countries ON people.country1 = countries.id
JOIN root_countries AS countries2 ON people.country2 = countries.id

Answer 3

SELECT 
  people.first_name AS "First Name", 
  people.last_name AS "Last Name",
  countries.name AS "Country1",
  territories.name AS "Territory1",
  cities.name AS "City1",
  countries2.name AS "Country2",
  territories2.name AS "Territory2", 
  cities2.name AS "City2"
FROM 
   adb_people AS people
   JOIN root_cities AS cities ON people.city1 = cities.id
   jOIN root_cities AS cities2 people.city2 = cities2.id
   JOIN root_territories AS territories ON people.prov_state1 = territories.id
   JOIN root_territories AS territories2 ON people.prov_state2 = territories2.id
   JOIN root_countries AS countries ON people.country1 = countries.id
   JOIN root_countries AS countries2 ON people.country2 = countries2.id

MySQL在同一个表上加入多个连接？

3 个答案: