如何更新通過連接兩個表在MySQL

Question

我有3個表

1. iata_en表3列（CITY_NAME，COUNTRY_NAME，iata_code）
2. d_cities表3列（CITY_NAME，COUNTRY_ID，iata_code）
3. d_country表2的列（COUNTRY_ID，COUNTRY_NAME）

我想iata_code柱從表複製到iata_en表d_citites其中（iata_en.cityname = d_cities.cityname）和iata_en.countryname = d_cities.country_nam e）

• 所以我加入了d_cities和d_country與外鍵得到 country_name。

我寫這篇文章的代碼，但它不工作

UPDATE d_cities 
     SET iata_code=iata_en.iata_code 
     FROM iata_en,d_cities as ci 
     INNER JOIN d_country as co 
     ON ci.CountryID=co.CountryID 
     WHERE iata_en.city_name=ci.city 
     AND iata_en.country_name=co.country 

Answer 1

所有表引用必須將UPDATE子句中，如果你指定甚至實際上並沒有更新它們。

UPDATE 
    d_cities 
    JOIN d_country USING (CountryID) 
    JOIN iata_en ON (
     city_name = city 
     AND country_name = country 
    ) 
SET 
    d_cities.iata_code = iata_en.iata_code 

Answer 2

嘗試此查詢：

UPDATE D_CITIES CITIES 
JOIN D_COUNTRY COUNTRY ON COUNTRY.COUNTRY_ID = CITIES.COUNTRY_ID 
JOIN IATA_EN IATA ON IATA.CITY_NAME = CITIES.CITY_NAME 
SET CITIES.IATA_CODE = IATA.IATA_CODE;