如何通过在mysql中连接两个表来更新

Question

我有3张桌子

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列（country_id，country_name）

我想将iata_code列从表iata_en复制到d_citites表，其中（iata_en.cityname = d_cities.cityname）和iata_en.countryname = d_cities.country_name）

• 所以我加入d_cities和d_country用外键来获取 COUNTRY_NAME。

我写了这段代码，但它不起作用

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

所有表引用都必须在UPDATE子句中指定，即使您实际上没有更新它们。

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

尝试此查询：

 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;